Remove locking from FFmpegDemuxerStream and associated TODOs from media code.

media/filters/ffmpeg_video_decoder.cc

Index: media/filters/ffmpeg_video_decoder.cc
diff --git a/media/filters/ffmpeg_video_decoder.cc b/media/filters/ffmpeg_video_decoder.cc
index d75782f94922b0aba3d46b0f8b94c44edac4be3f..db70580f66c29ad96275c21975cfa78295da2f25 100644
--- a/media/filters/ffmpeg_video_decoder.cc
+++ b/media/filters/ffmpeg_video_decoder.cc
@@ -251,25 +251,21 @@ void FFmpegVideoDecoder::ReadFromDemuxerStream() {
   DCHECK_NE(state_, kDecodeFinished);
   DCHECK(!read_cb_.is_null());
 
-  demuxer_stream_->Read(base::Bind(&FFmpegVideoDecoder::DecryptOrDecodeBuffer,
-                                   this));
-}
-
-void FFmpegVideoDecoder::DecryptOrDecodeBuffer(
-    DemuxerStream::Status status,
-    const scoped_refptr<DecoderBuffer>& buffer) {
-  DCHECK_EQ(status != DemuxerStream::kOk, !buffer) << status;
-  // TODO(scherkus): fix FFmpegDemuxerStream::Read() to not execute our read
-  // callback on the same execution stack so we can get rid of forced task post.
-  message_loop_->PostTask(FROM_HERE, base::Bind(
-      &FFmpegVideoDecoder::DoDecryptOrDecodeBuffer, this, status, buffer));
+  demuxer_stream_->Read(base::Bind(
+      &FFmpegVideoDecoder::DoDecryptOrDecodeBuffer, this));
 }
 
 void FFmpegVideoDecoder::DoDecryptOrDecodeBuffer(
     DemuxerStream::Status status,
     const scoped_refptr<DecoderBuffer>& buffer) {
-  DCHECK(message_loop_->BelongsToCurrentThread());
+  if (!message_loop_->BelongsToCurrentThread()) {
+    message_loop_->PostTask(FROM_HERE, base::Bind(
+        &FFmpegVideoDecoder::DoDecryptOrDecodeBuffer, this, status, buffer));
+    return;
+  }
+
   DCHECK_NE(state_, kDecodeFinished);
+  DCHECK_EQ(status != DemuxerStream::kOk, !buffer) << status;
 
   if (state_ == kUninitialized)
     return;