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 EnterDecodingState() {
    VideoDecoder::DecoderStatus status;
    scoped_refptr<VideoFrame> video_frame;
    DecodeSingleFrame(i_frame_buffer_, &status, &video_frame);

    EXPECT_EQ(status, VideoDecoder::kOk);
    ASSERT_TRUE(video_frame);
    EXPECT_FALSE(video_frame->IsEndOfStream());
  }

  void EnterDecodingState() {
    VideoDecoder::DecoderStatus status;
    scoped_refptr<VideoFrame> video_frame;
    DecodeSingleFrame(i_frame_buffer_, &status, &video_frame);

    EXPECT_EQ(status, VideoDecoder::kOk);
    ASSERT_TRUE(video_frame);
    EXPECT_FALSE(video_frame->IsEndOfStream());
  }
