GitLab

Expose a way for unit tests to terminate the AudioManager singleton to avoid conflicts between tests.
This fixes occasional crashes when running audio tests manually (won't happen on the bots right now since they don't have the required hardware).

TEST=Run content tests with --gtest_filter=*WebRTC* --gtest_repeat=1000
BUG=none
Review URL: http://codereview.chromium.org/8558022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@111586 0039d316-1c4b-4281-b951-d872f2087c98