update_engine: Populate UpdateCheckParams with rollback policies.

These are the policies introduced in crrev.com/c/916563,
controlling what should happen if target_version_prefix is
earlier than the current Chrome OS version, and how long Chrome
OS rollback protection should be postponed.

BUG=chromium:813036
TEST='cros_run_unit_tests --board=cyan --packages update_engine'

Change-Id: I33cf3b8975b52ca4b647a4b69a2d7879a9115d3c
Reviewed-on: https://chromium-review.googlesource.com/929321
Commit-Ready: Marton Hunyady <hunyadym@chromium.org>
Tested-by: Marton Hunyady <hunyadym@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/update_manager/chromeos_policy_unittest.cc b/update_manager/chromeos_policy_unittest.cc
index df29e8c..9538c4e 100644
--- a/update_manager/chromeos_policy_unittest.cc
+++ b/update_manager/chromeos_policy_unittest.cc
@@ -189,8 +189,14 @@
   // Override specific device policy attributes.
   fake_state_.device_policy_provider()->var_target_version_prefix()->
       reset(new string("1.2"));
-  fake_state_.device_policy_provider()->var_release_channel_delegated()->
-      reset(new bool(false));
+  fake_state_.device_policy_provider()->var_rollback_to_target_version()->reset(
+      new RollbackToTargetVersion(
+          RollbackToTargetVersion::kRollbackWithFullPowerwash));
+  fake_state_.device_policy_provider()
+      ->var_rollback_allowed_milestones()
+      ->reset(new int(5));
+  fake_state_.device_policy_provider()->var_release_channel_delegated()->reset(
+      new bool(false));
   fake_state_.device_policy_provider()->var_release_channel()->
       reset(new string("foo-channel"));
 
@@ -199,6 +205,9 @@
                      &Policy::UpdateCheckAllowed, &result);
   EXPECT_TRUE(result.updates_enabled);
   EXPECT_EQ("1.2", result.target_version_prefix);
+  EXPECT_EQ(RollbackToTargetVersion::kRollbackWithFullPowerwash,
+            result.rollback_to_target_version);
+  EXPECT_EQ(5, result.rollback_allowed_milestones);
   EXPECT_EQ("foo-channel", result.target_channel);
   EXPECT_FALSE(result.is_interactive);
 }