Add flag for restricting downloads

This adds a flag that can be used to turn off the ability to download
and apply updates from the API.  This value applies to all future
update checks that the update_engine performs.  Changing this value
during an update check has no effect on the current update check.

Bug: 66016687
Test: unit-tests, manual OTA

Change-Id: I655adf23cae44c63079bfa9dc18ba8ca65d7a304
(cherry picked from commit e22f2ddfec92623d38efbf17c17917f68e52907a)
diff --git a/update_attempter.h b/update_attempter.h
index 6b2a7a7..758494a 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -66,6 +66,7 @@
                         public PostinstallRunnerAction::DelegateInterface {
  public:
   using UpdateStatus = update_engine::UpdateStatus;
+  using UpdateAttemptFlags = update_engine::UpdateAttemptFlags;
   static const int kMaxDeltaUpdateFailures;
 
   UpdateAttempter(SystemState* system_state,
@@ -130,6 +131,20 @@
   int http_response_code() const { return http_response_code_; }
   void set_http_response_code(int code) { http_response_code_ = code; }
 
+  // Set flags that influence how updates and checks are performed.  These
+  // influence all future checks and updates until changed or the device
+  // reboots.
+  void SetUpdateAttemptFlags(UpdateAttemptFlags flags) {
+    update_attempt_flags_ = flags;
+  }
+
+  // Returns the update attempt flags that are in place for the current update
+  // attempt.  These are cached at the start of an update attempt so that they
+  // remain constant throughout the process.
+  virtual UpdateAttemptFlags GetCurrentUpdateAttemptFlags() {
+    return current_update_attempt_flags_;
+  }
+
   // This is the internal entry point for going through an
   // update. If the current status is idle invokes Update.
   // This is called by the DBus implementation.
@@ -259,6 +274,7 @@
   FRIEND_TEST(UpdateAttempterTest, ScheduleErrorEventActionNoEventTest);
   FRIEND_TEST(UpdateAttempterTest, ScheduleErrorEventActionTest);
   FRIEND_TEST(UpdateAttempterTest, TargetVersionPrefixSetAndReset);
+  FRIEND_TEST(UpdateAttempterTest, UpdateAttemptFlagsCachedAtUpdateStart);
   FRIEND_TEST(UpdateAttempterTest, UpdateDeferredByPolicyTest);
   FRIEND_TEST(UpdateAttempterTest, UpdateIsNotRunningWhenUpdateAvailable);
   FRIEND_TEST(UpdateAttempterTest, UpdateTest);
@@ -439,6 +455,11 @@
   std::string new_version_ = "0.0.0.0";
   std::string new_system_version_;
   uint64_t new_payload_size_ = 0;
+  // Flags influencing all periodic update checks
+  UpdateAttemptFlags update_attempt_flags_ = UpdateAttemptFlags::kNone;
+  // Flags influencing the currently in-progress check (cached at the start of
+  // the update check).
+  UpdateAttemptFlags current_update_attempt_flags_ = UpdateAttemptFlags::kNone;
 
   // Common parameters for all Omaha requests.
   OmahaRequestParams* omaha_request_params_ = nullptr;