Revert 124817 - Take extensions out of Profile into a profile-keyed service, ExtensionSystem.

Revert 124817 - Take extensions out of Profile into a profile-keyed service, ExtensionSystem.

This may be causing this crash:
Note: Google Test filter = PrerenderBrowserTest.PrerenderUnload
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from PrerenderBrowserTest, where TypeParam = 
[ RUN      ] PrerenderBrowserTest.PrerenderUnload
[2464:2324:0302/211059:6709843:FATAL:profile_dependency_manager.cc(134)] Check failed: false. Attempted to access a Profile that was ShutDown(). This is most likely a heap smasher in progress. After ProfileKeyedService::Shutdown() completes, your service MUST NOT refer to depended Profile services again.


Move InitExtensions into ExtensionSystem.
Remove a few accessors (ExtensionDevToolsManager, ExtensionMessageService). The others have too many callers to fix in one go.

BUG=104095
TEST=Open and close an incognito window; should not crash.


Review URL: http://codereview.chromium.org/9369013

TBR=yoz@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=124831