MediaStream API: Leaving Source/core/platform
Moving all the MediaStream API files from Source/code/platform to their
proper place. A pretty big patch but everything, with one exception, is
just moving, changing header includes and changing compiler defines.
The one exception is MediaStreamTrackSourcesRequest where I had to add
an interface (MediaStreamTrackSourcesRequestImpl) as to keep the
distiction between modules/ and platform/

Review URL: https://codereview.chromium.org/147273002

git-svn-id: svn://svn.chromium.org/blink/trunk@165817 bbb929c8-8fbe-4397-9dbb-9b2b20218538