GitLab

These methods currently all have a static variable that caches the queried value.
This causes a problem in unit tests where values can change between tests.
I moved them outside of the AudioDevice class and grouped in their own namespace
which owns the globally cached state and allows the cache to be invalidated.

R=henrika
TEST=Run *WebRTC* tests in content.
Review URL: http://codereview.chromium.org/8588030

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@110695 0039d316-1c4b-4281-b951-d872f2087c98