Push API: Log registration success/failure codes to UMA

Push API: Log registration success/failure codes to UMA

BUG=401438
Committed: https://crrev.com/1f125f14e0d2cb8980049baf43f1cb34d7307a4e
Cr-Commit-Position: refs/heads/master@{#300532}

[johnme, 2014-10-17 17:30:56]

johnme@chromium.org changed reviewers:
+ isherman@chromium.org, jochen@chromium.org

[johnme, 2014-10-17 17:30:58]

isherman@chromium.org: Please review changes in tools/metrics/histograms

jochen@chromium.org: Please review changes in content/

[Michael van Ouwerkerk, 2014-10-17 18:01:10]

mvanouwerkerk@chromium.org changed reviewers:
+ mvanouwerkerk@chromium.org

[Michael van Ouwerkerk, 2014-10-17 18:01:11]

lgtm for Push API changes, but I'm not an owner

[Ilya Sherman, 2014-10-17 22:38:37]

Histograms LGTM.

[jochen (gone - plz use gerrit), 2014-10-20 13:37:50]

lgtm

[johnme, 2014-10-21 15:25:05]

The CQ bit was checked by johnme@chromium.org

[commit-bot: I haz the power, 2014-10-21 15:25:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/644913006/1

[commit-bot: I haz the power, 2014-10-21 17:19:36]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-10-21 17:19:37]

Try jobs failed on following builders:
  linux_chromium_rel_swarming on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[johnme, 2014-10-21 18:23:51]

The CQ bit was checked by johnme@chromium.org

[commit-bot: I haz the power, 2014-10-21 18:25:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/644913006/1

[commit-bot: I haz the power, 2014-10-21 19:09:04]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-21 19:09:53]

Patchset 1 (id:??) landed as
https://crrev.com/1f125f14e0d2cb8980049baf43f1cb34d7307a4e
Cr-Commit-Position: refs/heads/master@{#300532}