update_engine: Report VPD write failure to UMA

Currently we see many first actives to come from non-FSI images. But we have not
been able to figure out why. This CL, reports a new error
kFirstActiveOmahaPingSentPersistenceError when writing the first active omaha
flag into VPD fails. This allows us to see if that is the actual cause of the
problem.

CL:1062659 adds the enum value on the Chrome side.

BUG=chromium:833980
TEST=unittests
TEST=precq

Change-Id: I65e233c5f895489ba905494fb20d7b00d0c4af10
Reviewed-on: https://chromium-review.googlesource.com/1062662
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
diff --git a/metrics_reporter_interface.h b/metrics_reporter_interface.h
index 2c7ce5b..13f5a54 100644
--- a/metrics_reporter_interface.h
+++ b/metrics_reporter_interface.h
@@ -193,6 +193,12 @@
   //
   // |kMetricInstallDateProvisioningSource|
   virtual void ReportInstallDateProvisioningSource(int source, int max) = 0;
+
+  // Helper function to report an internal error code. The following metrics are
+  // reported:
+  //
+  // |kMetricAttemptInternalErrorCode|
+  virtual void ReportInternalErrorCode(ErrorCode error_code) = 0;
 };
 
 }  // namespace chromeos_update_engine