Simplify shutdown of AudioDevice's audio thread.
This is a followup change for bug 107933 (see code review 9112029) that does the following:
* Makes Stop() asynchronous.
* Simplifies shutdown of AudioDevice's audio thread by always doing it from the IO thread.
* Simplifies access to of most member variables (added documentation).
* We no longer need synchronisation with the IO thread when shutting down the audio thread since we'll always shut it down from the IO thread.
* We don't need a lock to guard the audio_thread_ variable (and others related ones), since they're only modifed on the IO thread when the audio thread is not running.
I checked the implementations of AudioDevice::RenderCallback if this is OK and it should be fine.
BUG=107933
TEST=Run media and content tests
Review URL: https://chromiumcodereview.appspot.com/9264013
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@118810 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed
