Change VideoDecoder::ReadCB to take const scoped_refptr<VideoFrame>&.

BUG=none
TEST=media_unittests, media layout tests.


Review URL: https://chromiumcodereview.appspot.com/10559074

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@143192 0039d316-1c4b-4281-b951-d872f2087c98
void VideoRendererBase::SetPlaybackRate(float playback_rate) {
  base::AutoLock auto_lock(lock_);
  playback_rate_ = playback_rate;
}

void VideoRendererBase::SetPlaybackRate(float playback_rate) {
  base::AutoLock auto_lock(lock_);
  playback_rate_ = playback_rate;
}
