Move ExtensionActionStorageManager out of extension_action_api.*

Move ExtensionActionStorageManager out of extension_action_api.*

There's really no reason to have these in the same file, and it's cluttering it
up.

Bonus:
- Convert ExtensionActionStorageManager to use a BrowserContext.
- Remove ExtensionActionStorageManager's ExtensionService dependency.
- Remove ExtensionActionStorageManager's public weak ptr interface
- Consolidate extension_misc:: ExtensionAction icon stuff and ExtensionActionAPI
  icon stuff.

BUG=407290
Committed: https://crrev.com/2813c1b0f610548451d05287d81a342cb46754c1
Cr-Commit-Position: refs/heads/master@{#292036}

[Devlin, 2014-08-25 20:49:57]

Yoyo, please take a look when you can. :)

[Yoyo Zhou, 2014-08-26 19:19:18]

LGTM

[Devlin, 2014-08-26 21:08:16]

Patchset #2 (id:40001) has been deleted

[Devlin, 2014-08-26 21:20:45]

The CQ bit was checked by rdevlin.cronin@chromium.org

[commit-bot: I haz the power, 2014-08-26 21:22:12]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/rdevlin.cronin@chromium.org/502033003/...

[commit-bot: I haz the power, 2014-08-26 22:55:56]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_chromium_x64_rel_swarming on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[commit-bot: I haz the power, 2014-08-26 23:51:26]

Committed patchset #2 (60001) as 7155dd4af17411c8a37461bca2b181f70a97d435

[commit-bot: I haz the power, 2014-09-10 02:47:32]

Patchset 2 (id:??) landed as
https://crrev.com/2813c1b0f610548451d05287d81a342cb46754c1
Cr-Commit-Position: refs/heads/master@{#292036}