[ServiceWorkerCache] Reland backend state CL

[ServiceWorkerCache] Reland backend state CL

Reland of: https://codereview.chromium.org/701403002/
Reverted here: https://codereview.chromium.org/709003003/

InitDone() made an illegal state transition from BACKEND_CLOSED to BACKEND_OPEN.  I removed that transition, which means that pending operations will exit early instead of complete, so I updated the test expectations.

I also added some new testing framework to be able to delay not only cache backend creation but backend functions themselves, so far only OpenEntry.  This is used to recreate the dcheck crash discovered by the layout tests in https://crbug.com/431163

I don't intend to commit until after branch cut as this CL is mostly code cleanup and new tests.

BUG=430884
Committed: https://crrev.com/6d719ce3c33f68f79a80a034363c7749e9fed756
Cr-Commit-Position: refs/heads/master@{#303648}

[jkarlin, 2014-11-07 18:14:31]

Patchset #1 (id:1) has been deleted

[jkarlin, 2014-11-07 18:14:39]

Patchset #1 (id:20001) has been deleted

[jkarlin, 2014-11-07 19:42:46]

jkarlin@chromium.org changed reviewers:
+ falken@chromium.org, michaeln@chromium.org

[jkarlin, 2014-11-07 19:42:47]

michaeln@chromium.org: Please review changes in all

falken@chromium.org: Please review changes in all

Thanks!

[michaeln1, 2014-11-08 00:10:48]

michaeln@google.com changed reviewers:
+ michaeln@google.com

[michaeln1, 2014-11-08 00:10:49]

lgtm

[michaeln, 2014-11-08 00:11:19]

michaeln@chromium.org changed reviewers:
- michaeln@google.com

[michaeln, 2014-11-08 00:12:02]

and not surprisingly lgtm 2

[jkarlin, 2014-11-10 19:16:39]

The CQ bit was checked by jkarlin@chromium.org

[commit-bot: I haz the power, 2014-11-10 19:17:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/692993005/120001

[jkarlin, 2014-11-10 19:45:30]

The CQ bit was unchecked by jkarlin@chromium.org

[jkarlin, 2014-11-11 14:52:08]

The CQ bit was checked by jkarlin@chromium.org

[commit-bot: I haz the power, 2014-11-11 14:52:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/692993005/120001

[commit-bot: I haz the power, 2014-11-11 14:53:20]

Committed patchset #5 (id:120001)

[commit-bot: I haz the power, 2014-11-11 14:54:00]

Patchset 5 (id:??) landed as
https://crrev.com/6d719ce3c33f68f79a80a034363c7749e9fed756
Cr-Commit-Position: refs/heads/master@{#303648}