Policy for AndroidThings
am: 56d8ab3749

Change-Id: Ifd040710c3154e63b062098530b518b46ee90d22
diff --git a/Android.mk b/Android.mk
index 6a23168..2470865 100644
--- a/Android.mk
+++ b/Android.mk
@@ -305,10 +305,14 @@
     proxy_resolver.cc \
     real_system_state.cc \
     update_attempter.cc \
+    update_manager/android_things_policy.cc \
     update_manager/boxed_value.cc \
-    update_manager/chromeos_policy.cc \
     update_manager/default_policy.cc \
+    update_manager/enough_slots_ab_updates_policy_impl.cc \
     update_manager/evaluation_context.cc \
+    update_manager/interactive_update_policy_impl.cc \
+    update_manager/next_update_check_policy_impl.cc \
+    update_manager/official_build_check_policy_impl.cc \
     update_manager/policy.cc \
     update_manager/real_config_provider.cc \
     update_manager/real_device_policy_provider.cc \
@@ -969,10 +973,14 @@
     payload_state_unittest.cc \
     parcelable_update_engine_status_unittest.cc \
     update_attempter_unittest.cc \
+    update_manager/android_things_policy_unittest.cc \
     update_manager/boxed_value_unittest.cc \
+    update_manager/chromeos_policy.cc \
     update_manager/chromeos_policy_unittest.cc \
     update_manager/evaluation_context_unittest.cc \
     update_manager/generic_variables_unittest.cc \
+    update_manager/next_update_check_policy_impl_unittest.cc \
+    update_manager/policy_test_utils.cc \
     update_manager/prng_unittest.cc \
     update_manager/real_device_policy_provider_unittest.cc \
     update_manager/real_random_provider_unittest.cc \
diff --git a/update_manager/android_things_policy.cc b/update_manager/android_things_policy.cc
new file mode 100644
index 0000000..2304f12
--- /dev/null
+++ b/update_manager/android_things_policy.cc
@@ -0,0 +1,152 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/android_things_policy.h"
+
+#include <string>
+#include <vector>
+
+#include <base/logging.h>
+#include <base/time/time.h>
+
+#include "update_engine/update_manager/enough_slots_ab_updates_policy_impl.h"
+#include "update_engine/update_manager/interactive_update_policy_impl.h"
+#include "update_engine/update_manager/official_build_check_policy_impl.h"
+
+using base::Time;
+using chromeos_update_engine::ErrorCode;
+using std::string;
+using std::vector;
+
+namespace chromeos_update_manager {
+
+const NextUpdateCheckPolicyConstants
+    AndroidThingsPolicy::kNextUpdateCheckPolicyConstants = {
+        .timeout_initial_interval = 7 * 60,
+        .timeout_periodic_interval = 5 * 60 * 60,
+        .timeout_max_backoff_interval = 26 * 60 * 60,
+        .timeout_regular_fuzz = 10 * 60,
+        .attempt_backoff_max_interval_in_days = 16,
+        .attempt_backoff_fuzz_in_hours = 12,
+};
+
+EvalStatus AndroidThingsPolicy::UpdateCheckAllowed(
+    EvaluationContext* ec,
+    State* state,
+    string* error,
+    UpdateCheckParams* result) const {
+  // Set the default return values.
+  result->updates_enabled = true;
+  result->target_channel.clear();
+  result->target_version_prefix.clear();
+  result->is_interactive = false;
+
+  // Build a list of policies to consult.  Note that each policy may modify the
+  // result structure, even if it signals kContinue.
+  EnoughSlotsAbUpdatesPolicyImpl enough_slots_ab_updates_policy;
+  OnlyUpdateOfficialBuildsPolicyImpl only_update_official_builds_policy;
+  InteractiveUpdatePolicyImpl interactive_update_policy;
+  NextUpdateCheckTimePolicyImpl next_update_check_time_policy(
+      kNextUpdateCheckPolicyConstants);
+
+  vector<Policy const*> policies_to_consult = {
+      // Do not perform any updates if there are not enough slots to do
+      // A/B updates
+      &enough_slots_ab_updates_policy,
+
+      // Unofficial builds should not perform periodic update checks.
+      &only_update_official_builds_policy,
+
+      // Check to see if an interactive update was requested.
+      &interactive_update_policy,
+
+      // Ensure that periodic update checks are timed properly.
+      &next_update_check_time_policy,
+  };
+
+  // Now that the list of policy implementations, and the order to consult them,
+  // as been setup, do that.  If none of the policies make a definitive
+  // decisions about whether or not to check for updates, then allow the update
+  // check to happen.
+  EvalStatus status = ConsultPolicies(policies_to_consult,
+                                      &Policy::UpdateCheckAllowed,
+                                      ec,
+                                      state,
+                                      error,
+                                      result);
+  if (status != EvalStatus::kContinue) {
+    return status;
+  } else {
+    // It is time to check for an update.
+    LOG(INFO) << "Allowing update check.";
+    return EvalStatus::kSucceeded;
+  }
+}
+
+// Always returns |EvalStatus::kSucceeded|
+EvalStatus AndroidThingsPolicy::UpdateCanBeApplied(
+    EvaluationContext* ec,
+    State* state,
+    string* error,
+    chromeos_update_engine::ErrorCode* result,
+    chromeos_update_engine::InstallPlan* install_plan) const {
+  *result = ErrorCode::kSuccess;
+  return EvalStatus::kSucceeded;
+}
+
+// Always returns |EvalStatus::kSucceeded|
+EvalStatus AndroidThingsPolicy::UpdateCanStart(EvaluationContext* ec,
+                                               State* state,
+                                               string* error,
+                                               UpdateDownloadParams* result,
+                                               UpdateState update_state) const {
+  // Update is good to go.
+  result->update_can_start = true;
+  return EvalStatus::kSucceeded;
+}
+
+// Always returns |EvalStatus::kSucceeded|
+EvalStatus AndroidThingsPolicy::UpdateDownloadAllowed(EvaluationContext* ec,
+                                                      State* state,
+                                                      string* error,
+                                                      bool* result) const {
+  // By default, we allow updates.
+  *result = true;
+  return EvalStatus::kSucceeded;
+}
+
+// P2P is always disabled.  Returns |result|==|false| and
+// |EvalStatus::kSucceeded|
+EvalStatus AndroidThingsPolicy::P2PEnabled(EvaluationContext* ec,
+                                           State* state,
+                                           string* error,
+                                           bool* result) const {
+  *result = false;
+  return EvalStatus::kSucceeded;
+}
+
+// This will return immediately with |EvalStatus::kSucceeded| and set
+// |result|==|false|
+EvalStatus AndroidThingsPolicy::P2PEnabledChanged(EvaluationContext* ec,
+                                                  State* state,
+                                                  string* error,
+                                                  bool* result,
+                                                  bool prev_result) const {
+  *result = false;
+  return EvalStatus::kSucceeded;
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/android_things_policy.h b/update_manager/android_things_policy.h
new file mode 100644
index 0000000..6f8f4ad
--- /dev/null
+++ b/update_manager/android_things_policy.h
@@ -0,0 +1,91 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_ANDROID_THINGS_POLICY_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_ANDROID_THINGS_POLICY_H_
+
+#include <string>
+
+#include "update_engine/update_manager/next_update_check_policy_impl.h"
+#include "update_engine/update_manager/policy_utils.h"
+
+namespace chromeos_update_manager {
+
+// AndroidThingsPolicy implements the policy-related logic used in
+// AndroidThings.
+class AndroidThingsPolicy : public Policy {
+ public:
+  AndroidThingsPolicy() = default;
+  ~AndroidThingsPolicy() override = default;
+
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override;
+
+  // Always returns |EvalStatus::kSucceeded|
+  EvalStatus UpdateCanBeApplied(
+      EvaluationContext* ec,
+      State* state,
+      std::string* error,
+      chromeos_update_engine::ErrorCode* result,
+      chromeos_update_engine::InstallPlan* install_plan) const override;
+
+  // Always returns |EvalStatus::kSucceeded|
+  EvalStatus UpdateCanStart(EvaluationContext* ec,
+                            State* state,
+                            std::string* error,
+                            UpdateDownloadParams* result,
+                            UpdateState update_state) const override;
+
+  // Always returns |EvalStatus::kSucceeded|
+  EvalStatus UpdateDownloadAllowed(EvaluationContext* ec,
+                                   State* state,
+                                   std::string* error,
+                                   bool* result) const override;
+
+  // P2P is always disabled.  Returns |result|==|false| and
+  // |EvalStatus::kSucceeded|
+  virtual EvalStatus P2PEnabled(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                bool* result) const override;
+
+  // This will return immediately with |EvalStatus::kSucceeded| and set
+  // |result|==|false|
+  virtual EvalStatus P2PEnabledChanged(EvaluationContext* ec,
+                                       State* state,
+                                       std::string* error,
+                                       bool* result,
+                                       bool prev_result) const override;
+
+ protected:
+  // Policy override.
+  std::string PolicyName() const override { return "AndroidThingsPolicy"; }
+
+ private:
+  friend class UmAndroidThingsPolicyTest;
+  FRIEND_TEST(UmAndroidThingsPolicyTest, UpdateCheckAllowedWaitsForTheTimeout);
+
+  static const NextUpdateCheckPolicyConstants kNextUpdateCheckPolicyConstants;
+
+  DISALLOW_COPY_AND_ASSIGN(AndroidThingsPolicy);
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_ANDROID_THINGS_POLICY_H_
diff --git a/update_manager/android_things_policy_unittest.cc b/update_manager/android_things_policy_unittest.cc
new file mode 100644
index 0000000..8b7d128
--- /dev/null
+++ b/update_manager/android_things_policy_unittest.cc
@@ -0,0 +1,156 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/android_things_policy.h"
+
+#include "update_engine/update_manager/next_update_check_policy_impl.h"
+#include "update_engine/update_manager/policy_test_utils.h"
+
+using base::Time;
+using base::TimeDelta;
+
+namespace chromeos_update_manager {
+
+class UmAndroidThingsPolicyTest : public UmPolicyTestBase {
+ protected:
+  UmAndroidThingsPolicyTest() {
+    policy_ = std::make_unique<AndroidThingsPolicy>();
+  }
+
+  void SetUpDefaultState() override {
+    UmPolicyTestBase::SetUpDefaultState();
+
+    // For the purpose of the tests, this is an official build
+    fake_state_.system_provider()->var_is_official_build()->reset(
+        new bool(true));
+    fake_state_.system_provider()->var_num_slots()->reset(new unsigned int(2));
+  }
+
+  // Configures the policy to return a desired value from UpdateCheckAllowed by
+  // faking the current wall clock time as needed. Restores the default state.
+  // This is used when testing policies that depend on this one.
+  virtual void SetUpdateCheckAllowed(bool allow_check) {
+    Time next_update_check;
+    CallMethodWithContext(&NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+                          &next_update_check,
+                          AndroidThingsPolicy::kNextUpdateCheckPolicyConstants);
+    SetUpDefaultState();
+    Time curr_time = next_update_check;
+    if (allow_check)
+      curr_time += TimeDelta::FromSeconds(1);
+    else
+      curr_time -= TimeDelta::FromSeconds(1);
+    fake_clock_.SetWallclockTime(curr_time);
+  }
+};
+
+TEST_F(UmAndroidThingsPolicyTest, UpdateCheckAllowedWaitsForTheTimeout) {
+  // We get the next update_check timestamp from the policy's private method
+  // and then we check the public method respects that value on the normal
+  // case.
+  Time next_update_check;
+  Time last_checked_time =
+      fake_clock_.GetWallclockTime() + TimeDelta::FromMinutes(1234);
+
+  LOG(INFO) << "last_checked_time: " << last_checked_time;
+  fake_state_.updater_provider()->var_last_checked_time()->reset(
+      new Time(last_checked_time));
+  CallMethodWithContext(&NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+                        &next_update_check,
+                        AndroidThingsPolicy::kNextUpdateCheckPolicyConstants);
+  LOG(INFO) << "Next check allowed at: " << next_update_check;
+
+  // Check that the policy blocks until the next_update_check is reached.
+  SetUpDefaultClock();
+  SetUpDefaultState();
+  fake_state_.updater_provider()->var_last_checked_time()->reset(
+      new Time(last_checked_time));
+  fake_clock_.SetWallclockTime(next_update_check - TimeDelta::FromSeconds(1));
+
+  UpdateCheckParams result;
+  ExpectPolicyStatus(
+      EvalStatus::kAskMeAgainLater, &Policy::UpdateCheckAllowed, &result);
+
+  SetUpDefaultClock();
+  SetUpDefaultState();
+  fake_state_.updater_provider()->var_last_checked_time()->reset(
+      new Time(last_checked_time));
+  fake_clock_.SetWallclockTime(next_update_check + TimeDelta::FromSeconds(1));
+  ExpectPolicyStatus(
+      EvalStatus::kSucceeded, &Policy::UpdateCheckAllowed, &result);
+  EXPECT_TRUE(result.updates_enabled);
+  EXPECT_FALSE(result.is_interactive);
+}
+
+TEST_F(UmAndroidThingsPolicyTest,
+       UpdateCheckAllowedUpdatesDisabledForUnofficialBuilds) {
+  // UpdateCheckAllowed should return kAskMeAgainLater if this is an unofficial
+  // build; we don't want periodic update checks on developer images.
+
+  fake_state_.system_provider()->var_is_official_build()->reset(
+      new bool(false));
+
+  UpdateCheckParams result;
+  ExpectPolicyStatus(
+      EvalStatus::kAskMeAgainLater, &Policy::UpdateCheckAllowed, &result);
+}
+
+TEST_F(UmAndroidThingsPolicyTest,
+       UpdateCheckAllowedUpdatesDisabledWhenNotEnoughSlotsAbUpdates) {
+  // UpdateCheckAllowed should return false (kSucceeded) if the image booted
+  // without enough slots to do A/B updates.
+
+  fake_state_.system_provider()->var_num_slots()->reset(new unsigned int(1));
+
+  UpdateCheckParams result;
+  ExpectPolicyStatus(
+      EvalStatus::kSucceeded, &Policy::UpdateCheckAllowed, &result);
+  EXPECT_FALSE(result.updates_enabled);
+}
+
+TEST_F(UmAndroidThingsPolicyTest,
+       UpdateCheckAllowedForcedUpdateRequestedInteractive) {
+  // UpdateCheckAllowed should return true because a forced update request was
+  // signaled for an interactive update.
+
+  SetUpdateCheckAllowed(true);
+  fake_state_.updater_provider()->var_forced_update_requested()->reset(
+      new UpdateRequestStatus(UpdateRequestStatus::kInteractive));
+
+  UpdateCheckParams result;
+  ExpectPolicyStatus(
+      EvalStatus::kSucceeded, &Policy::UpdateCheckAllowed, &result);
+  EXPECT_TRUE(result.updates_enabled);
+  EXPECT_TRUE(result.is_interactive);
+}
+
+TEST_F(UmAndroidThingsPolicyTest,
+       UpdateCheckAllowedForcedUpdateRequestedPeriodic) {
+  // UpdateCheckAllowed should return true because a forced update request was
+  // signaled for a periodic check.
+
+  SetUpdateCheckAllowed(true);
+  fake_state_.updater_provider()->var_forced_update_requested()->reset(
+      new UpdateRequestStatus(UpdateRequestStatus::kPeriodic));
+
+  UpdateCheckParams result;
+  ExpectPolicyStatus(
+      EvalStatus::kSucceeded, &Policy::UpdateCheckAllowed, &result);
+  EXPECT_TRUE(result.updates_enabled);
+  EXPECT_FALSE(result.is_interactive);
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/chromeos_policy_unittest.cc b/update_manager/chromeos_policy_unittest.cc
index 0c38700..2cd2aa6 100644
--- a/update_manager/chromeos_policy_unittest.cc
+++ b/update_manager/chromeos_policy_unittest.cc
@@ -418,9 +418,9 @@
 }
 
 TEST_F(UmChromeOSPolicyTest,
-       UpdateCheckAllowedUpdatesDisabledForRemovableBootDevice) {
+       UpdateCheckAllowedUpdatesDisabledWhenNotEnoughSlotsAbUpdates) {
   // UpdateCheckAllowed should return false (kSucceeded) if the image booted
-  // from a removable device.
+  // without enough slots to do A/B updates.
 
   fake_state_.system_provider()->var_num_slots()->reset(new unsigned int(1));
 
diff --git a/update_manager/enough_slots_ab_updates_policy_impl.cc b/update_manager/enough_slots_ab_updates_policy_impl.cc
new file mode 100644
index 0000000..70f15d4
--- /dev/null
+++ b/update_manager/enough_slots_ab_updates_policy_impl.cc
@@ -0,0 +1,38 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/enough_slots_ab_updates_policy_impl.h"
+
+namespace chromeos_update_manager {
+
+// Do not perform any updates if booted from removable device. This decision
+// is final.
+EvalStatus EnoughSlotsAbUpdatesPolicyImpl::UpdateCheckAllowed(
+    EvaluationContext* ec,
+    State* state,
+    std::string* error,
+    UpdateCheckParams* result) const {
+  const auto* num_slots_p =
+      ec->GetValue(state->system_provider()->var_num_slots());
+  if (num_slots_p == nullptr || *num_slots_p < 2) {
+    LOG(INFO) << "Not enough slots for A/B updates, disabling update checks.";
+    result->updates_enabled = false;
+    return EvalStatus::kSucceeded;
+  }
+  return EvalStatus::kContinue;
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/enough_slots_ab_updates_policy_impl.h b/update_manager/enough_slots_ab_updates_policy_impl.h
new file mode 100644
index 0000000..c0701f8
--- /dev/null
+++ b/update_manager/enough_slots_ab_updates_policy_impl.h
@@ -0,0 +1,49 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_ENOUGH_SLOTS_AB_UPDATES_POLICY_IMPL_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_ENOUGH_SLOTS_AB_UPDATES_POLICY_IMPL_H_
+
+#include <string>
+
+#include "update_engine/update_manager/policy_utils.h"
+
+namespace chromeos_update_manager {
+
+// Do not perform any updates if booted from removable device.
+class EnoughSlotsAbUpdatesPolicyImpl : public PolicyImplBase {
+ public:
+  EnoughSlotsAbUpdatesPolicyImpl() = default;
+  ~EnoughSlotsAbUpdatesPolicyImpl() override = default;
+
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override;
+
+ protected:
+  std::string PolicyName() const override {
+    return "EnoughSlotsAbUpdatesPolicyImpl";
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(EnoughSlotsAbUpdatesPolicyImpl);
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_ENOUGH_SLOTS_AB_UPDATES_POLICY_IMPL_H_
\ No newline at end of file
diff --git a/update_manager/interactive_update_policy_impl.cc b/update_manager/interactive_update_policy_impl.cc
new file mode 100644
index 0000000..df7f17b
--- /dev/null
+++ b/update_manager/interactive_update_policy_impl.cc
@@ -0,0 +1,44 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/interactive_update_policy_impl.h"
+
+namespace chromeos_update_manager {
+
+// Check to see if an interactive update was requested.
+EvalStatus InteractiveUpdatePolicyImpl::UpdateCheckAllowed(
+    EvaluationContext* ec,
+    State* state,
+    std::string* error,
+    UpdateCheckParams* result) const {
+  UpdaterProvider* const updater_provider = state->updater_provider();
+
+  // First, check to see if an interactive update was requested.
+  const UpdateRequestStatus* forced_update_requested_p =
+      ec->GetValue(updater_provider->var_forced_update_requested());
+  if (forced_update_requested_p != nullptr &&
+      *forced_update_requested_p != UpdateRequestStatus::kNone) {
+    result->is_interactive =
+        (*forced_update_requested_p == UpdateRequestStatus::kInteractive);
+    LOG(INFO) << "Forced update signaled ("
+              << (result->is_interactive ? "interactive" : "periodic")
+              << "), allowing update check.";
+    return EvalStatus::kSucceeded;
+  }
+  return EvalStatus::kContinue;
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/interactive_update_policy_impl.h b/update_manager/interactive_update_policy_impl.h
new file mode 100644
index 0000000..fc68ea3
--- /dev/null
+++ b/update_manager/interactive_update_policy_impl.h
@@ -0,0 +1,49 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_INTERACTIVE_UPDATE_POLICY_IMPL_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_INTERACTIVE_UPDATE_POLICY_IMPL_H_
+
+#include <string>
+
+#include "update_engine/update_manager/policy_utils.h"
+
+namespace chromeos_update_manager {
+
+// Check to see if an interactive update was requested.
+class InteractiveUpdatePolicyImpl : public PolicyImplBase {
+ public:
+  InteractiveUpdatePolicyImpl() = default;
+  ~InteractiveUpdatePolicyImpl() override = default;
+
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override;
+
+ protected:
+  std::string PolicyName() const override {
+    return "InteractiveUpdatePolicyImpl";
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InteractiveUpdatePolicyImpl);
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_OFFICIAL_BUILD_CHECK_POLICY_IMPL_H_
\ No newline at end of file
diff --git a/update_manager/next_update_check_policy_impl.cc b/update_manager/next_update_check_policy_impl.cc
new file mode 100644
index 0000000..6f9748e
--- /dev/null
+++ b/update_manager/next_update_check_policy_impl.cc
@@ -0,0 +1,150 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/next_update_check_policy_impl.h"
+
+#include <algorithm>
+
+#include "update_engine/common/utils.h"
+
+using base::Time;
+using base::TimeDelta;
+using std::max;
+using std::string;
+
+namespace chromeos_update_manager {
+
+NextUpdateCheckTimePolicyImpl::NextUpdateCheckTimePolicyImpl(
+    const NextUpdateCheckPolicyConstants& constants)
+    : policy_constants_(constants) {}
+
+EvalStatus NextUpdateCheckTimePolicyImpl::UpdateCheckAllowed(
+    EvaluationContext* ec,
+    State* state,
+    string* error,
+    UpdateCheckParams* result) const {
+  // Ensure that periodic update checks are timed properly.
+  Time next_update_check;
+
+  if (NextUpdateCheckTime(
+          ec, state, error, &next_update_check, policy_constants_) !=
+      EvalStatus::kSucceeded) {
+    return EvalStatus::kFailed;
+  }
+  if (!ec->IsWallclockTimeGreaterThan(next_update_check)) {
+    LOG(INFO) << "Periodic check interval not satisfied, blocking until "
+              << chromeos_update_engine::utils::ToString(next_update_check);
+    return EvalStatus::kAskMeAgainLater;
+  }
+
+  return EvalStatus::kContinue;
+}
+
+EvalStatus NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime(
+    EvaluationContext* ec,
+    State* state,
+    string* error,
+    Time* next_update_check,
+    const NextUpdateCheckPolicyConstants& constants) {
+  UpdaterProvider* const updater_provider = state->updater_provider();
+
+  // Don't check for updates too often. We limit the update checks to once every
+  // some interval. The interval is kTimeoutInitialInterval the first time and
+  // kTimeoutPeriodicInterval for the subsequent update checks. If the update
+  // check fails, we increase the interval between the update checks
+  // exponentially until kTimeoutMaxBackoffInterval. Finally, to avoid having
+  // many chromebooks running update checks at the exact same time, we add some
+  // fuzz to the interval.
+  const Time* updater_started_time =
+      ec->GetValue(updater_provider->var_updater_started_time());
+  POLICY_CHECK_VALUE_AND_FAIL(updater_started_time, error);
+
+  const Time* last_checked_time =
+      ec->GetValue(updater_provider->var_last_checked_time());
+
+  const auto* seed = ec->GetValue(state->random_provider()->var_seed());
+  POLICY_CHECK_VALUE_AND_FAIL(seed, error);
+
+  PRNG prng(*seed);
+
+  // If this is the first attempt, compute and return an initial value.
+  if (last_checked_time == nullptr ||
+      *last_checked_time < *updater_started_time) {
+    *next_update_check = *updater_started_time +
+                         FuzzedInterval(&prng,
+                                        constants.timeout_initial_interval,
+                                        constants.timeout_regular_fuzz);
+    return EvalStatus::kSucceeded;
+  }
+
+  // Check whether the server is enforcing a poll interval; if not, this value
+  // will be zero.
+  const unsigned int* server_dictated_poll_interval =
+      ec->GetValue(updater_provider->var_server_dictated_poll_interval());
+  POLICY_CHECK_VALUE_AND_FAIL(server_dictated_poll_interval, error);
+
+  int interval = *server_dictated_poll_interval;
+  int fuzz = 0;
+
+  // If no poll interval was dictated by server compute a back-off period,
+  // starting from a predetermined base periodic interval and increasing
+  // exponentially by the number of consecutive failed attempts.
+  if (interval == 0) {
+    const unsigned int* consecutive_failed_update_checks =
+        ec->GetValue(updater_provider->var_consecutive_failed_update_checks());
+    POLICY_CHECK_VALUE_AND_FAIL(consecutive_failed_update_checks, error);
+
+    interval = constants.timeout_periodic_interval;
+    unsigned int num_failures = *consecutive_failed_update_checks;
+    while (interval < constants.timeout_max_backoff_interval && num_failures) {
+      interval *= 2;
+      num_failures--;
+    }
+  }
+
+  // We cannot back off longer than the predetermined maximum interval.
+  if (interval > constants.timeout_max_backoff_interval)
+    interval = constants.timeout_max_backoff_interval;
+
+  // We cannot back off shorter than the predetermined periodic interval. Also,
+  // in this case set the fuzz to a predetermined regular value.
+  if (interval <= constants.timeout_periodic_interval) {
+    interval = constants.timeout_periodic_interval;
+    fuzz = constants.timeout_regular_fuzz;
+  }
+
+  // If not otherwise determined, defer to a fuzz of +/-(interval / 2).
+  if (fuzz == 0)
+    fuzz = interval;
+
+  *next_update_check =
+      *last_checked_time + FuzzedInterval(&prng, interval, fuzz);
+  return EvalStatus::kSucceeded;
+}
+
+TimeDelta NextUpdateCheckTimePolicyImpl::FuzzedInterval(PRNG* prng,
+                                                        int interval,
+                                                        int fuzz) {
+  DCHECK_GE(interval, 0);
+  DCHECK_GE(fuzz, 0);
+  int half_fuzz = fuzz / 2;
+  // This guarantees the output interval is non negative.
+  int interval_min = max(interval - half_fuzz, 0);
+  int interval_max = interval + half_fuzz;
+  return TimeDelta::FromSeconds(prng->RandMinMax(interval_min, interval_max));
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/next_update_check_policy_impl.h b/update_manager/next_update_check_policy_impl.h
new file mode 100644
index 0000000..d9f3c3b
--- /dev/null
+++ b/update_manager/next_update_check_policy_impl.h
@@ -0,0 +1,98 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_NEXT_UPDATE_CHECK_POLICY_IMPL_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_NEXT_UPDATE_CHECK_POLICY_IMPL_H_
+
+#include <string>
+
+#include <base/time/time.h>
+
+#include "update_engine/update_manager/policy_utils.h"
+#include "update_engine/update_manager/prng.h"
+
+namespace chromeos_update_manager {
+
+// Constants that are provided to the policy implementation.
+struct NextUpdateCheckPolicyConstants {
+  // Default update check timeout interval/fuzz values used to compute the
+  // NextUpdateCheckTime(), in seconds. Actual fuzz is within +/- half of the
+  // indicated value.
+  int timeout_initial_interval;
+  int timeout_periodic_interval;
+  int timeout_max_backoff_interval;
+  int timeout_regular_fuzz;
+
+  // Maximum update attempt backoff interval and fuzz.
+  int attempt_backoff_max_interval_in_days;
+  int attempt_backoff_fuzz_in_hours;
+};
+
+// Ensure that periodic update checks are timed properly.
+class NextUpdateCheckTimePolicyImpl : public PolicyImplBase {
+ public:
+  explicit NextUpdateCheckTimePolicyImpl(
+      const NextUpdateCheckPolicyConstants& constants);
+
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override;
+
+  // A private policy implementation returning the wallclock timestamp when
+  // the next update check should happen.
+  // TODO(garnold) We should probably change that to infer a monotonic
+  // timestamp, which will make the update check intervals more resilient to
+  // clock skews. Might require switching some of the variables exported by the
+  // UpdaterProvider to report monotonic time, as well.
+  //
+  // NOTE:
+  // Exposed as a public static so that it's logic can be used to test
+  // Policy implementations that utilize this fragment for their
+  // timing, without needing to list them all with FRIEND_TEST (so that
+  // those Policy implementations can exist without modifying this
+  // class's definition.
+  //
+  // The output value from this method (|next_update_check|), isn't
+  // available via the UpdateCheckParams |result| of the Policy
+  // method, and so this timing logic needs to be otherwise exposed.
+  static EvalStatus NextUpdateCheckTime(
+      EvaluationContext* ec,
+      State* state,
+      std::string* error,
+      base::Time* next_update_check,
+      const NextUpdateCheckPolicyConstants& constants);
+
+  // Returns a TimeDelta based on the provided |interval| seconds +/- half
+  // |fuzz| seconds. The return value is guaranteed to be a non-negative
+  // TimeDelta.
+  static base::TimeDelta FuzzedInterval(PRNG* prng, int interval, int fuzz);
+
+ protected:
+  std::string PolicyName() const override {
+    return "NextUpdateCheckTimePolicyImpl";
+  }
+
+ private:
+  const NextUpdateCheckPolicyConstants policy_constants_;
+
+  DISALLOW_COPY_AND_ASSIGN(NextUpdateCheckTimePolicyImpl);
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_NEXT_UPDATE_CHECK_POLICY_IMPL_H_
\ No newline at end of file
diff --git a/update_manager/next_update_check_policy_impl_unittest.cc b/update_manager/next_update_check_policy_impl_unittest.cc
new file mode 100644
index 0000000..ddc88e7
--- /dev/null
+++ b/update_manager/next_update_check_policy_impl_unittest.cc
@@ -0,0 +1,161 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/next_update_check_policy_impl.h"
+
+#include "update_engine/update_manager/policy_test_utils.h"
+
+using base::Time;
+using base::TimeDelta;
+using std::string;
+
+namespace chromeos_update_manager {
+
+const NextUpdateCheckPolicyConstants policy_test_constants = {
+    // these are specifically NOT the values used by real Policy
+    // implementations.
+    .timeout_initial_interval = 3 * 60,
+    .timeout_periodic_interval = 2 * 60 * 60,
+    .timeout_max_backoff_interval = 8 * 60 * 60,
+    .timeout_regular_fuzz = 5 * 60,
+    .attempt_backoff_max_interval_in_days = 12,
+    .attempt_backoff_fuzz_in_hours = 10,
+};
+
+class UmNextUpdateCheckTimePolicyImplTest : public UmPolicyTestBase {
+ protected:
+  UmNextUpdateCheckTimePolicyImplTest() {
+    policy_ =
+        std::make_unique<NextUpdateCheckTimePolicyImpl>(policy_test_constants);
+  }
+};
+
+TEST_F(UmNextUpdateCheckTimePolicyImplTest,
+       FirstCheckIsAtMostInitialIntervalAfterStart) {
+  Time next_update_check;
+
+  // Set the last update time so it'll appear as if this is a first update check
+  // in the lifetime of the current updater.
+  fake_state_.updater_provider()->var_last_checked_time()->reset(
+      new Time(fake_clock_.GetWallclockTime() - TimeDelta::FromMinutes(10)));
+
+  CallMethodWithContext(&NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+                        &next_update_check,
+                        policy_test_constants);
+
+  EXPECT_LE(fake_clock_.GetWallclockTime(), next_update_check);
+  EXPECT_GE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(
+                    policy_test_constants.timeout_initial_interval +
+                    policy_test_constants.timeout_regular_fuzz / 2),
+            next_update_check);
+}
+
+TEST_F(UmNextUpdateCheckTimePolicyImplTest, RecurringCheckBaseIntervalAndFuzz) {
+  // Ensure that we're using the correct interval (kPeriodicInterval) and fuzz
+  // (ktimeout_regular_fuzz) as base values for period updates.
+  Time next_update_check;
+
+  CallMethodWithContext(&NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+                        &next_update_check,
+                        policy_test_constants);
+
+  EXPECT_LE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(
+                    policy_test_constants.timeout_periodic_interval -
+                    policy_test_constants.timeout_regular_fuzz / 2),
+            next_update_check);
+  EXPECT_GE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(
+                    policy_test_constants.timeout_periodic_interval +
+                    policy_test_constants.timeout_regular_fuzz / 2),
+            next_update_check);
+}
+
+TEST_F(UmNextUpdateCheckTimePolicyImplTest,
+       RecurringCheckBackoffIntervalAndFuzz) {
+  // Ensure that we're properly backing off and fuzzing in the presence of
+  // failed updates attempts.
+  Time next_update_check;
+
+  fake_state_.updater_provider()->var_consecutive_failed_update_checks()->reset(
+      new unsigned int(2));
+
+  ExpectStatus(EvalStatus::kSucceeded,
+               NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+               &next_update_check,
+               policy_test_constants);
+
+  int expected_interval = policy_test_constants.timeout_periodic_interval * 4;
+  EXPECT_LE(
+      fake_clock_.GetWallclockTime() +
+          TimeDelta::FromSeconds(expected_interval - expected_interval / 2),
+      next_update_check);
+  EXPECT_GE(
+      fake_clock_.GetWallclockTime() +
+          TimeDelta::FromSeconds(expected_interval + expected_interval / 2),
+      next_update_check);
+}
+
+TEST_F(UmNextUpdateCheckTimePolicyImplTest,
+       RecurringCheckServerDictatedPollInterval) {
+  // Policy honors the server provided check poll interval.
+  Time next_update_check;
+
+  const auto kInterval = policy_test_constants.timeout_periodic_interval * 4;
+  fake_state_.updater_provider()->var_server_dictated_poll_interval()->reset(
+      new unsigned int(kInterval));
+  // We should not be backing off in this case.
+  fake_state_.updater_provider()->var_consecutive_failed_update_checks()->reset(
+      new unsigned int(2));
+
+  ExpectStatus(EvalStatus::kSucceeded,
+               &NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+               &next_update_check,
+               policy_test_constants);
+
+  EXPECT_LE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(kInterval - kInterval / 2),
+            next_update_check);
+  EXPECT_GE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(kInterval + kInterval / 2),
+            next_update_check);
+}
+
+TEST_F(UmNextUpdateCheckTimePolicyImplTest, ExponentialBackoffIsCapped) {
+  Time next_update_check;
+
+  fake_state_.updater_provider()->var_consecutive_failed_update_checks()->reset(
+      new unsigned int(100));
+
+  ExpectStatus(EvalStatus::kSucceeded,
+               &NextUpdateCheckTimePolicyImpl::NextUpdateCheckTime,
+               &next_update_check,
+               policy_test_constants);
+
+  EXPECT_LE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(
+                    policy_test_constants.timeout_max_backoff_interval -
+                    policy_test_constants.timeout_max_backoff_interval / 2),
+            next_update_check);
+  EXPECT_GE(fake_clock_.GetWallclockTime() +
+                TimeDelta::FromSeconds(
+                    policy_test_constants.timeout_max_backoff_interval +
+                    policy_test_constants.timeout_max_backoff_interval / 2),
+            next_update_check);
+}
+
+}  // namespace chromeos_update_manager
\ No newline at end of file
diff --git a/update_manager/official_build_check_policy_impl.cc b/update_manager/official_build_check_policy_impl.cc
new file mode 100644
index 0000000..096f7bf
--- /dev/null
+++ b/update_manager/official_build_check_policy_impl.cc
@@ -0,0 +1,36 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/official_build_check_policy_impl.h"
+
+namespace chromeos_update_manager {
+
+// Unofficial builds should not perform periodic update checks.
+EvalStatus OnlyUpdateOfficialBuildsPolicyImpl::UpdateCheckAllowed(
+    EvaluationContext* ec,
+    State* state,
+    std::string* error,
+    UpdateCheckParams* result) const {
+  const bool* is_official_build_p =
+      ec->GetValue(state->system_provider()->var_is_official_build());
+  if (is_official_build_p != nullptr && !(*is_official_build_p)) {
+    LOG(INFO) << "Unofficial build, blocking periodic update checks.";
+    return EvalStatus::kAskMeAgainLater;
+  }
+  return EvalStatus::kContinue;
+}
+
+}  // namespace chromeos_update_manager
diff --git a/update_manager/official_build_check_policy_impl.h b/update_manager/official_build_check_policy_impl.h
new file mode 100644
index 0000000..deb81c3
--- /dev/null
+++ b/update_manager/official_build_check_policy_impl.h
@@ -0,0 +1,49 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_OFFICIAL_BUILD_CHECK_POLICY_IMPL_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_OFFICIAL_BUILD_CHECK_POLICY_IMPL_H_
+
+#include <string>
+
+#include "update_engine/update_manager/policy_utils.h"
+
+namespace chromeos_update_manager {
+
+// Unofficial builds should not perform periodic update checks.
+class OnlyUpdateOfficialBuildsPolicyImpl : public PolicyImplBase {
+ public:
+  OnlyUpdateOfficialBuildsPolicyImpl() = default;
+  ~OnlyUpdateOfficialBuildsPolicyImpl() override = default;
+
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override;
+
+ protected:
+  std::string PolicyName() const override {
+    return "OnlyUpdateOfficialBuildsPolicyImpl";
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(OnlyUpdateOfficialBuildsPolicyImpl);
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_OFFICIAL_BUILD_CHECK_POLICY_IMPL_H_
\ No newline at end of file
diff --git a/update_manager/policy.cc b/update_manager/policy.cc
index 151c225..5f79a68 100644
--- a/update_manager/policy.cc
+++ b/update_manager/policy.cc
@@ -30,6 +30,8 @@
       return "kSucceeded";
     case EvalStatus::kAskMeAgainLater:
       return "kAskMeAgainLater";
+    case EvalStatus::kContinue:
+      return "kContinue";
   }
   return "Invalid";
 }
diff --git a/update_manager/policy.h b/update_manager/policy.h
index c2fc358..b60c4da 100644
--- a/update_manager/policy.h
+++ b/update_manager/policy.h
@@ -33,6 +33,7 @@
   kFailed,
   kSucceeded,
   kAskMeAgainLater,
+  kContinue,
 };
 
 std::string ToString(EvalStatus status);
diff --git a/update_manager/policy_test_utils.cc b/update_manager/policy_test_utils.cc
new file mode 100644
index 0000000..dfeb2d4
--- /dev/null
+++ b/update_manager/policy_test_utils.cc
@@ -0,0 +1,109 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/update_manager/policy_test_utils.h"
+
+#include <tuple>
+#include <vector>
+
+#include "update_engine/update_manager/next_update_check_policy_impl.h"
+
+using base::Time;
+using base::TimeDelta;
+using chromeos_update_engine::ErrorCode;
+using std::string;
+using std::tuple;
+using std::vector;
+
+namespace chromeos_update_manager {
+
+void UmPolicyTestBase::SetUp() {
+  loop_.SetAsCurrent();
+  SetUpDefaultClock();
+  eval_ctx_ = new EvaluationContext(&fake_clock_, TimeDelta::FromSeconds(5));
+  SetUpDefaultState();
+}
+
+void UmPolicyTestBase::TearDown() {
+  EXPECT_FALSE(loop_.PendingTasks());
+}
+
+// Sets the clock to fixed values.
+void UmPolicyTestBase::SetUpDefaultClock() {
+  fake_clock_.SetMonotonicTime(Time::FromInternalValue(12345678L));
+  fake_clock_.SetWallclockTime(Time::FromInternalValue(12345678901234L));
+}
+
+void UmPolicyTestBase::SetUpDefaultState() {
+  fake_state_.updater_provider()->var_updater_started_time()->reset(
+      new Time(fake_clock_.GetWallclockTime()));
+  fake_state_.updater_provider()->var_last_checked_time()->reset(
+      new Time(fake_clock_.GetWallclockTime()));
+  fake_state_.updater_provider()->var_consecutive_failed_update_checks()->reset(
+      new unsigned int(0));
+  fake_state_.updater_provider()->var_server_dictated_poll_interval()->reset(
+      new unsigned int(0));
+  fake_state_.updater_provider()->var_forced_update_requested()->reset(
+      new UpdateRequestStatus{UpdateRequestStatus::kNone});
+
+  // Chosen by fair dice roll.  Guaranteed to be random.
+  fake_state_.random_provider()->var_seed()->reset(new uint64_t(4));
+}
+
+// Returns a default UpdateState structure:
+UpdateState UmPolicyTestBase::GetDefaultUpdateState(
+    TimeDelta first_seen_period) {
+  Time first_seen_time = fake_clock_.GetWallclockTime() - first_seen_period;
+  UpdateState update_state = UpdateState();
+
+  // This is a non-interactive check returning a delta payload, seen for the
+  // first time (|first_seen_period| ago). Clearly, there were no failed
+  // attempts so far.
+  update_state.is_interactive = false;
+  update_state.is_delta_payload = false;
+  update_state.first_seen = first_seen_time;
+  update_state.num_checks = 1;
+  update_state.num_failures = 0;
+  update_state.failures_last_updated = Time();  // Needs to be zero.
+  // There's a single HTTP download URL with a maximum of 10 retries.
+  update_state.download_urls = vector<string>{"http://fake/url/"};
+  update_state.download_errors_max = 10;
+  // Download was never attempted.
+  update_state.last_download_url_idx = -1;
+  update_state.last_download_url_num_errors = 0;
+  // There were no download errors.
+  update_state.download_errors = vector<tuple<int, ErrorCode, Time>>();
+  // P2P is not disabled by Omaha.
+  update_state.p2p_downloading_disabled = false;
+  update_state.p2p_sharing_disabled = false;
+  // P2P was not attempted.
+  update_state.p2p_num_attempts = 0;
+  update_state.p2p_first_attempted = Time();
+  // No active backoff period, backoff is not disabled by Omaha.
+  update_state.backoff_expiry = Time();
+  update_state.is_backoff_disabled = false;
+  // There is no active scattering wait period (max 7 days allowed) nor check
+  // threshold (none allowed).
+  update_state.scatter_wait_period = TimeDelta();
+  update_state.scatter_check_threshold = 0;
+  update_state.scatter_wait_period_max = TimeDelta::FromDays(7);
+  update_state.scatter_check_threshold_min = 0;
+  update_state.scatter_check_threshold_max = 0;
+
+  return update_state;
+}
+
+}  // namespace chromeos_update_manager
\ No newline at end of file
diff --git a/update_manager/policy_test_utils.h b/update_manager/policy_test_utils.h
new file mode 100644
index 0000000..09b2550
--- /dev/null
+++ b/update_manager/policy_test_utils.h
@@ -0,0 +1,98 @@
+//
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_UPDATE_MANAGER_POLICY_TEST_UTILS_H_
+#define UPDATE_ENGINE_UPDATE_MANAGER_POLICY_TEST_UTILS_H_
+
+#include <string>
+
+#include <base/time/time.h>
+#include <brillo/message_loops/fake_message_loop.h>
+#include <gtest/gtest.h>
+
+#include "update_engine/common/fake_clock.h"
+#include "update_engine/update_manager/evaluation_context.h"
+#include "update_engine/update_manager/fake_state.h"
+#include "update_engine/update_manager/policy_utils.h"
+
+namespace chromeos_update_manager {
+
+class UmPolicyTestBase : public ::testing::Test {
+ protected:
+  explicit UmPolicyTestBase() = default;
+
+  void SetUp() override;
+
+  void TearDown() override;
+
+  // Sets the clock to fixed values.
+  virtual void SetUpDefaultClock();
+
+  // Sets up the default state in fake_state_.  override to add Policy-specific
+  // items, but only after calling this class's implementation.
+  virtual void SetUpDefaultState();
+
+  // Returns a default UpdateState structure:
+  virtual UpdateState GetDefaultUpdateState(base::TimeDelta first_seen_period);
+
+  // Runs the passed |method| after resetting the EvaluationContext and expects
+  // it to return the |expected| return value.
+  template <typename T, typename R, typename... Args>
+  void ExpectStatus(EvalStatus expected, T method, R* result, Args... args) {
+    std::string error = "<None>";
+    eval_ctx_->ResetEvaluation();
+    EXPECT_EQ(expected,
+              (*method)(eval_ctx_.get(), &fake_state_, &error, result, args...))
+        << "Returned error: " << error
+        << "\nEvaluation context: " << eval_ctx_->DumpContext();
+  }
+
+  // Runs the passed |method| after resetting the EvaluationContext, in order
+  // to use the method to get a value for other testing (doesn't validate the
+  // return value, just returns it).
+  template <typename T, typename R, typename... Args>
+  EvalStatus CallMethodWithContext(T method, R* result, Args... args) {
+    std::string error = "<None>";
+    eval_ctx_->ResetEvaluation();
+    return (*method)(eval_ctx_.get(), &fake_state_, &error, result, args...);
+  }
+
+  // Runs the passed |policy_method| on the framework policy and expects it to
+  // return the |expected| return value.
+  template <typename T, typename R, typename... Args>
+  void ExpectPolicyStatus(EvalStatus expected,
+                          T policy_method,
+                          R* result,
+                          Args... args) {
+    std::string error = "<None>";
+    eval_ctx_->ResetEvaluation();
+    EXPECT_EQ(expected,
+              (policy_.get()->*policy_method)(
+                  eval_ctx_.get(), &fake_state_, &error, result, args...))
+        << "Returned error: " << error
+        << "\nEvaluation context: " << eval_ctx_->DumpContext();
+  }
+
+  brillo::FakeMessageLoop loop_{nullptr};
+  chromeos_update_engine::FakeClock fake_clock_;
+  FakeState fake_state_;
+  scoped_refptr<EvaluationContext> eval_ctx_;
+  std::unique_ptr<Policy> policy_;
+};
+
+}  // namespace chromeos_update_manager
+
+#endif  // UPDATE_ENGINE_UPDATE_MANAGER_POLICY_TEST_UTILS_H_
\ No newline at end of file
diff --git a/update_manager/policy_utils.h b/update_manager/policy_utils.h
index 960987e..e448022 100644
--- a/update_manager/policy_utils.h
+++ b/update_manager/policy_utils.h
@@ -35,4 +35,84 @@
       } \
     } while (false)
 
+namespace chromeos_update_manager {
+
+// Call the passed-in Policy method on a series of Policy implementations, until
+// one of them renders a decision by returning a value other than
+// |EvalStatus::kContinue|.
+template <typename T, typename R, typename... Args>
+EvalStatus ConsultPolicies(const std::vector<Policy const*> policies,
+                           T policy_method,
+                           EvaluationContext* ec,
+                           State* state,
+                           std::string* error,
+                           R* result,
+                           Args... args) {
+  for (auto policy : policies) {
+    EvalStatus status =
+        (policy->*policy_method)(ec, state, error, result, args...);
+    if (status != EvalStatus::kContinue) {
+      LOG(INFO) << "decision by " << policy->PolicyRequestName(policy_method);
+      return status;
+    }
+  }
+  return EvalStatus::kContinue;
+};
+
+// Base class implementation that returns |EvalStatus::kContinue| for all
+// decisions, to be used as a base-class for various Policy facets that only
+// pertain to certain situations. This might be better folded into Policy
+// instead of using pure-virtual methods on that class.
+class PolicyImplBase : public Policy {
+ public:
+  // Policy overrides.
+  EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
+                                State* state,
+                                std::string* error,
+                                UpdateCheckParams* result) const override {
+    return EvalStatus::kContinue;
+  };
+
+  EvalStatus UpdateCanBeApplied(
+      EvaluationContext* ec,
+      State* state,
+      std::string* error,
+      chromeos_update_engine::ErrorCode* result,
+      chromeos_update_engine::InstallPlan* install_plan) const override {
+    return EvalStatus::kContinue;
+  };
+
+  EvalStatus UpdateCanStart(EvaluationContext* ec,
+                            State* state,
+                            std::string* error,
+                            UpdateDownloadParams* result,
+                            UpdateState update_state) const override {
+    return EvalStatus::kContinue;
+  };
+
+  EvalStatus UpdateDownloadAllowed(EvaluationContext* ec,
+                                   State* state,
+                                   std::string* error,
+                                   bool* result) const override {
+    return EvalStatus::kContinue;
+  };
+
+  EvalStatus P2PEnabled(EvaluationContext* ec,
+                        State* state,
+                        std::string* error,
+                        bool* result) const override {
+    return EvalStatus::kContinue;
+  };
+
+  EvalStatus P2PEnabledChanged(EvaluationContext* ec,
+                               State* state,
+                               std::string* error,
+                               bool* result,
+                               bool prev_result) const override {
+    return EvalStatus::kContinue;
+  };
+};
+
+}  // namespace chromeos_update_manager
+
 #endif  // UPDATE_ENGINE_UPDATE_MANAGER_POLICY_UTILS_H_
diff --git a/update_manager/update_manager.cc b/update_manager/update_manager.cc
index 8e9b221..25f3216 100644
--- a/update_manager/update_manager.cc
+++ b/update_manager/update_manager.cc
@@ -16,7 +16,11 @@
 
 #include "update_engine/update_manager/update_manager.h"
 
+#ifdef __ANDROID__
+#include "update_engine/update_manager/android_things_policy.h"
+#else
 #include "update_engine/update_manager/chromeos_policy.h"
+#endif  // __ANDROID__
 #include "update_engine/update_manager/state.h"
 
 namespace chromeos_update_manager {
@@ -28,9 +32,11 @@
         evaluation_timeout_(evaluation_timeout),
         expiration_timeout_(expiration_timeout),
         weak_ptr_factory_(this) {
-  // TODO(deymo): Make it possible to replace this policy with a different
-  // implementation with a build-time flag.
+#ifdef __ANDROID__
+  policy_.reset(new AndroidThingsPolicy());
+#else
   policy_.reset(new ChromeOSPolicy());
+#endif  // __ANDROID__
 }
 
 UpdateManager::~UpdateManager() {