Revert 208403 "Remove MediaStreamDeviceThread in favor of using ..."

Revert 208403 "Remove MediaStreamDeviceThread in favor of using ..."

> Remove MediaStreamDeviceThread in favor of using AudioThread.
> 
> Doesn't seem to be a good reason for this thread; remove it in favor
> of using the thread provided by the AudioManager.
> 
> This also ensures we don't issue CoreAudio calls on a thread other
> than the main thread for OSX.
> 
> Bonus: Making this change required converting several unittests to use
> the new TestBrowserThreadBundle instead of manually creating threads.
> 
> BUG=158170, 256945
> TEST=unit tests pass. device changes work.
> 
> Review URL: https://chromiumcodereview.appspot.com/17444005

This leaves in the UMA statistics and test cleanup and only reverts the
device thread removal.

TBR=dalecurtis@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=210027

[DaleCurtis, 2013-07-03 19:51:08]

Committed patchset #2 manually as r210027 (presubmit successful).