gpu: Always subscribe to SurfaceTexture frame updates in StreamTexture

Always subscribe to the OnFrameAvailable callback from the underlying
SurfaceTexture in StreamTexture. This ensures StreamTexture always knows
whether a new frame is available or not, regardless of whether its
client is interested in frame updates or not. In particular, this lets
us read a texture from a hidden video element.

Note that the client still needs to use alternate means of
synchronization to determine whether a frame has been produced into the
SurfaceTexture. In the case of the video element, the onPrepared()
signal from the media player is used for this purpose.

BUG=306485
TEST=content/test/gpu/run_gpu_test --browser=android-chrome run webgl_conformance --page-filter=.*npot-video.*

Review URL: https://codereview.chromium.org/158723008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250700 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250700
Use BrowserMessageFilter instead of WorkerMessageFilter in WorkerDocumentSet.

We will use WorkerDocumentSet for other type of BrowserMessageFilter while moving SharedWorker to the renderer process.

BUG=327256

Review URL: https://codereview.chromium.org/159893008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250701 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250701