Convert ExtensionRegistry to a BrowserContextKeyedService

Convert ExtensionRegistry to a BrowserContextKeyedService

This removes dependencies on ExtensionService, which does not exist for
app_shell.

* Convert all of src/extensions to use ExtensionRegistry's extension sets.
* Remove ExtensionService::blacklisted_extensions() and convert all callers
  to use ExtensionRegistry.

BUG=none
TEST=existing unit_tests, browser_tests
R=miket@chromium.org
TBR=phajden.jr@chromium.org for adding dependency on components/browser_context_keyed_service

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=242624

[James Cook, 2013-12-27 01:00:27]

Ben, PTAL.  This is the BCKS conversion we talked about last week.  Once this
lands I'll be able to avoid using ExtensionService in a few more places and get
app_shell closer to starting up an extension.

https://codereview.chromium.org/120863003/diff/1/chrome/browser/extensions/ex...
File chrome/browser/extensions/extension_service.h (right):

https://codereview.chromium.org/120863003/diff/1/chrome/browser/extensions/ex...
chrome/browser/extensions/extension_service.h:166: const
extensions::ExtensionSet* terminated_extensions() const;
I'll get rid of this soon - doing it now would make this CL too big.

https://codereview.chromium.org/120863003/diff/1/chrome/browser/extensions/ex...
chrome/browser/extensions/extension_service.h:745:
extensions::ExtensionRegistry* registry_;
I decided to keep this pointer because there are a bunch of registry lookups in
the .cc file and it seemed more readable to use this than calling
ExtensionRegistry::Get() every time.

[James Cook, 2013-12-27 17:07:21]

miket, can you take a look?  I'm blocked on this patch landing.

[miket_OOO, 2013-12-27 17:12:23]

lgtm

[James Cook, 2013-12-27 17:44:05]

Committed patchset #1 manually as r242624 (presubmit successful).