Move extensions storage API implementation to src/extensions

Move extensions storage API implementation to src/extensions

This moves the core functionality (frontend, backend and local storage
implementations) to src/extensions while leaving Chrome-specific sync storage
and managed storage implementations in src/chrome.

BUG=348058
TEST=unit_tests *Storage*:*Settings* browser_tests ExtensionSettings*
TBR=zea@chromium.org for header file move touching chrome/browser/sync/test/integration/extension_settings_helper.cc

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=255901

[James Cook, 2014-03-07 21:21:02]

Devlin, PTAL.  This is mostly a mechanical move with a little bit of #include
cleanup.

https://codereview.chromium.org/189263013/diff/1/extensions/browser/DEPS
File extensions/browser/DEPS (right):

https://codereview.chromium.org/189263013/diff/1/extensions/browser/DEPS#newc...
extensions/browser/DEPS:37: # http://crbug.com/348058
This will happen after rockot's patch https://codereview.chromium.org/183893041/
lands, which adds support for idl files in src/extensions.

[Devlin, 2014-03-07 22:34:39]

lgtm.

It looks like rockot's is in the CQ now - so can I assume the DEPS will be
updated before this goes in?

[James Cook, 2014-03-07 22:42:57]

I can wait until his lands, or land this independently and do the IDL move in
another CL.  Do you have a preference?

[Devlin, 2014-03-07 22:44:00]

On 2014/03/07 22:42:57, James Cook wrote:
> I can wait until his lands, or land this independently and do the IDL move in
> another CL.  Do you have a preference?

Nope, whatever's easier for you.

[James Cook, 2014-03-09 16:03:38]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-03-09 16:03:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/189263013/10001

[commit-bot: I haz the power, 2014-03-09 17:40:25]

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

[commit-bot: I haz the power, 2014-03-09 17:40:26]

Retried try job too often on win_rel for step(s) unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[James Cook, 2014-03-10 04:16:18]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-03-10 04:16:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/189263013/10001

[commit-bot: I haz the power, 2014-03-10 07:20:22]

Change committed as 255901