update_engine: Add powerwash flag to update status

Add a powerwash flag to the update status which is set to true if and
only if a powerwash takes place. This will ensure that the user is
informed of a pending powerwash exactly when it is going to happen.

BUG=chromium:1070563
TEST=FEATURES=test emerge-amd64-generic update_engine
channel change and update on test device

Cq-Depend: chromium:2187671
Change-Id: I58314ecc7c9c2e64c906ef5b31cb780948196296
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2187672
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Tested-by: Miriam Polzer <mpolzer@google.com>
Commit-Queue: Miriam Polzer <mpolzer@google.com>
diff --git a/update_attempter.h b/update_attempter.h
index e270b59..1bf552b 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -265,9 +265,11 @@
   FRIEND_TEST(UpdateAttempterTest, DisableDeltaUpdateIfNeededTest);
   FRIEND_TEST(UpdateAttempterTest, DownloadProgressAccumulationTest);
   FRIEND_TEST(UpdateAttempterTest, InstallSetsStatusIdle);
-  FRIEND_TEST(UpdateAttempterTest, IsEnterpriseRollbackInGetStatusDefault);
   FRIEND_TEST(UpdateAttempterTest, IsEnterpriseRollbackInGetStatusTrue);
   FRIEND_TEST(UpdateAttempterTest, IsEnterpriseRollbackInGetStatusFalse);
+  FRIEND_TEST(UpdateAttempterTest,
+              PowerwashInGetStatusTrueBecausePowerwashRequired);
+  FRIEND_TEST(UpdateAttempterTest, PowerwashInGetStatusTrueBecauseRollback);
   FRIEND_TEST(UpdateAttempterTest, MarkDeltaUpdateFailureTest);
   FRIEND_TEST(UpdateAttempterTest, PingOmahaTest);
   FRIEND_TEST(UpdateAttempterTest, ProcessingDoneInstallError);