Unrevert r141537: Add extensions::StateStore and use that instead of

Unrevert r141537: Add extensions::StateStore and use that instead of
ExtensionPrefs for persisting alarm state to disk.

More to come:
- context menus
- omnibox
- declarative webRequest

TBR=brettw
BUG=123366
TEST=extension alarms are still remembered after chrome restart

Change since last time: Fall back to a FailingValueStore if ValueStoreFrontend
can't open the database.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=141780

[Matt Perry, 2012-06-12 00:15:56]

http://codereview.chromium.org/10545128/diff/1/chrome/browser/value_store/val...
File chrome/browser/value_store/value_store_frontend.cc (right):

http://codereview.chromium.org/10545128/diff/1/chrome/browser/value_store/val...
chrome/browser/value_store/value_store_frontend.cc:66: storage_ = new
FailingValueStore();
This is the main difference.

I also renamed FailingSettingsStore to FailingValueStore. I must've missed that
the first time around.

[Yoyo Zhou, 2012-06-12 00:18:14]

LGTM