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/common/hardware_interface.h b/common/hardware_interface.h
index 4d7c162..239e7c8 100644
--- a/common/hardware_interface.h
+++ b/common/hardware_interface.h
@@ -110,9 +110,9 @@
   // |SetFirstActiveOmahaPingSent()|.
   virtual bool GetFirstActiveOmahaPingSent() const = 0;
 
-  // Persist the fact that first active ping was sent to omaha. It bails out if
-  // it fails.
-  virtual void SetFirstActiveOmahaPingSent() = 0;
+  // Persist the fact that first active ping was sent to omaha and returns false
+  // if failed to persist it.
+  virtual bool SetFirstActiveOmahaPingSent() = 0;
 };
 
 }  // namespace chromeos_update_engine