Measure current usage statistics for MediaStream label and stop() before going for deprecation.
As per spec, both label and stop have been deprecated.
Spec = http://dev.w3.org/2011/webrtc/editor/getusermedia.html#mediastream

BUG=407039

Review URL: https://codereview.chromium.org/535733005

git-svn-id: svn://svn.chromium.org/blink/trunk@182408 bbb929c8-8fbe-4397-9dbb-9b2b20218538