Small refactor to media architecture in order to allow end-to-end tests.
- Introduced the class MockAudioManager that will be used by upcoming speech recognition tests.
- Added interface TestAudioInputController::Delegate, which allows to intercept Record/Close events.
- Added audio_manager_for_tests_ static field in SpeechRecognizer to inject the MockAudioManager during tests.
BUG=116954
TEST=none
Review URL: https://chromiumcodereview.appspot.com/
10704154
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@146316 0039d316-1c4b-4281-b951-d872f2087c98