Service Worker: Don't record StartWorker metrics for a doomed worker.

Service Worker: Don't record StartWorker metrics for a doomed worker.

This happens a lot because the update check sees the worker is byte-by-byte
identical and then dooms the worker before it finishes starting.

BUG=448003
Committed: https://crrev.com/0c55bbd9a4936f01be865b2efb4eecd7201c5c40
Cr-Commit-Position: refs/heads/master@{#319854}

[falken, 2015-03-10 08:17:03]

falken@chromium.org changed reviewers:
+ kinuko@chromium.org, nhiroki@chromium.org

[falken, 2015-03-10 08:17:04]

PTL

[nhiroki, 2015-03-10 08:29:05]

lgtm

[falken, 2015-03-10 08:36:01]

The CQ bit was checked by falken@chromium.org

[commit-bot: I haz the power, 2015-03-10 08:36:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/995713002/20001

[commit-bot: I haz the power, 2015-03-10 09:44:10]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-10 09:44:38]

Patchset 2 (id:??) landed as
https://crrev.com/0c55bbd9a4936f01be865b2efb4eecd7201c5c40
Cr-Commit-Position: refs/heads/master@{#319854}