[ServiceWorkerCacheStorage] Add support for new Open method.

[ServiceWorkerCacheStorage] Add support for new Open method.

Create/Get have been replaced by Open which will first attempt to Get() followed by Create() if Get() failed.

CLs in this three-legged-patch:

*1. Add open to browser - https://codereview.chromium.org/664433003/
2. Add open (remove get/create) to Blink - https://codereview.chromium.org/638023003
3. Remove get/create from browser - https://codereview.chromium.org/663503002/

Note that the three CLs have been tested together and pass tests locally.

BUG=423942
Committed: https://crrev.com/56f997e36d2148a03cb11773644505345cdcf1f2
Cr-Commit-Position: refs/heads/master@{#300047}

[jkarlin, 2014-10-16 12:12:34]

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

[jkarlin, 2014-10-16 12:12:35]

falken@chromium.org: Please review changes in everything

michaeln@chromium.org: Please review changes in everything

tsepez@chromium.org: Please review changes in service_worker_messages.h

Thanks all!

[jkarlin, 2014-10-16 13:30:26]

Patchset #2 (id:20001) has been deleted

[Tom Sepez, 2014-10-16 16:40:30]

Messages LGTM.

[falken, 2014-10-17 01:34:33]

lgtm

[michaeln, 2014-10-17 01:45:52]

lgtm 2

[jkarlin, 2014-10-17 01:55:26]

The CQ bit was checked by jkarlin@chromium.org

[commit-bot: I haz the power, 2014-10-17 01:56:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/664433003/60001

[commit-bot: I haz the power, 2014-10-17 02:38:10]

Committed patchset #3 (id:60001)

[commit-bot: I haz the power, 2014-10-17 02:39:05]

Patchset 3 (id:??) landed as
https://crrev.com/56f997e36d2148a03cb11773644505345cdcf1f2
Cr-Commit-Position: refs/heads/master@{#300047}