PM: UpdaterProvider reports the number of consecutive failed update checks.

This adds a new variable to UpdaterProvider, along with the necessary
bits of implementation in UpdateAttempter, to track and report this
number.

BUG=chromium:367006
TEST=Unit tests.

Change-Id: I819dc5c9d4d351e5bfe1373dba0993e3f622b0e0
Reviewed-on: https://chromium-review.googlesource.com/197092
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/update_attempter_mock.h b/update_attempter_mock.h
index 29e46bc..d2bc447 100644
--- a/update_attempter_mock.h
+++ b/update_attempter_mock.h
@@ -28,6 +28,8 @@
                                int64_t* new_size));
 
   MOCK_METHOD1(GetBootTimeAtUpdate, bool(base::Time* out_boot_time));
+
+  MOCK_CONST_METHOD0(consecutive_failed_update_checks, unsigned int(void));
 };
 
 }  // namespace chromeos_update_engine