Remove reference counting from media::VideoDecoder and friends.

media/filters/gpu_video_decoder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/filters/gpu_video_decoder.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/cpu.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
+#include "base/task_runner_util.h"
 #include "media/base/bind_to_loop.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/pipeline.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/video_decoder_config.h"
 
 namespace media {
 
+// Proxies calls to a VideoDecodeAccelerator::Client from the calling thread to
+// the client's thread.
+//
+// TODO(scherkus): VDAClientProxy should hold onto GpuVideoDecoder::Factories
+// and take care of some of the work that GpuVideoDecoder does to minimize
+// thread hopping. See following for discussion:
+//
+// https://codereview.chromium.org/12989009/diff/27035/media/filters/gpu_video_decoder.cc#newcode23
+class VDAClientProxy
+    : public base::RefCountedThreadSafe<VDAClientProxy>,
+      public VideoDecodeAccelerator::Client {
+ public:
+  explicit VDAClientProxy(VideoDecodeAccelerator::Client* client);
+
+  // Detaches the proxy. |client| will no longer be called and can be safely

[xhwang, 2013/04/18 00:40:48]

s/client/weak_client_/ ?

[scherkus (not reviewing), 2013/04/18 18:45:29]

Done.

+  // deleted. Any pending/future calls will be discarded.
+  //
+  // Must be called on |client_loop|.

[xhwang, 2013/04/18 00:40:48]

s/client_loop/client_loop_/

[scherkus (not reviewing), 2013/04/18 18:45:29]

Done.

+  void Detach();
+
+  // VideoDecodeAccelerator::Client implementation.
+  virtual void NotifyInitializeDone() OVERRIDE;
+  virtual void ProvidePictureBuffers(uint32 count,
+                                     const gfx::Size& size,
+                                     uint32 texture_target) OVERRIDE;
+  virtual void DismissPictureBuffer(int32 id) OVERRIDE;
+  virtual void PictureReady(const media::Picture& picture) OVERRIDE;
+  virtual void NotifyEndOfBitstreamBuffer(int32 id) OVERRIDE;
+  virtual void NotifyFlushDone() OVERRIDE;
+  virtual void NotifyResetDone() OVERRIDE;
+  virtual void NotifyError(media::VideoDecodeAccelerator::Error error) OVERRIDE;
+
+ private:
+  friend class base::RefCountedThreadSafe<VDAClientProxy>;
+  virtual ~VDAClientProxy();
+
+  scoped_refptr<base::MessageLoopProxy> client_loop_;
+
+  // Weak pointers are used to invalidate tasks posted to |client_loop_| that

[xhwang, 2013/04/18 00:40:48]

s/that/after ?

[scherkus (not reviewing), 2013/04/18 18:45:29]

Done.

+  // Detach() has been called.
+  base::WeakPtrFactory<VideoDecodeAccelerator::Client> weak_client_factory_;
+  base::WeakPtr<VideoDecodeAccelerator::Client> weak_client_;
+
+  DISALLOW_COPY_AND_ASSIGN(VDAClientProxy);
+};
+
+VDAClientProxy::VDAClientProxy(VideoDecodeAccelerator::Client* client)
+    : client_loop_(base::MessageLoopProxy::current()),
+      weak_client_factory_(client),
+      weak_client_(weak_client_factory_.GetWeakPtr()) {
+  DCHECK(weak_client_);
+}
+
+VDAClientProxy::~VDAClientProxy() {
+  DCHECK(!weak_client_) << "Detach() was not called";
+}
+
+void VDAClientProxy::Detach() {
+  DCHECK(client_loop_->BelongsToCurrentThread());
+  DCHECK(weak_client_) << "Detach() already called";
+  weak_client_factory_.InvalidateWeakPtrs();
+}
+
+void VDAClientProxy::NotifyInitializeDone() {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::NotifyInitializeDone, weak_client_));
+}
+
+void VDAClientProxy::ProvidePictureBuffers(uint32 count,
+                                           const gfx::Size& size,
+                                           uint32 texture_target) {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::ProvidePictureBuffers, weak_client_,
+      count, size, texture_target));
+}
+
+void VDAClientProxy::DismissPictureBuffer(int32 id) {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::DismissPictureBuffer, weak_client_, id));
+}
+
+void VDAClientProxy::PictureReady(const media::Picture& picture) {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::PictureReady, weak_client_, picture));
+}
+
+void VDAClientProxy::NotifyEndOfBitstreamBuffer(int32 id) {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::NotifyEndOfBitstreamBuffer, weak_client_,
+      id));
+}
+
+void VDAClientProxy::NotifyFlushDone() {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::NotifyFlushDone, weak_client_));
+}
+
+void VDAClientProxy::NotifyResetDone() {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::NotifyResetDone, weak_client_));
+}
+
+void VDAClientProxy::NotifyError(media::VideoDecodeAccelerator::Error error) {
+  client_loop_->PostTask(FROM_HERE, base::Bind(
+      &VideoDecodeAccelerator::Client::NotifyError, weak_client_, error));
+}
+
+
 // Maximum number of concurrent VDA::Decode() operations GVD will maintain.
 // Higher values allow better pipelining in the GPU, but also require more
 // resources.
 enum { kMaxInFlightDecodes = 4 };
 
 GpuVideoDecoder::Factories::~Factories() {}
 
 // Size of shared-memory segments we allocate.  Since we reuse them we let them
 // be on the beefy side.
 static const size_t kSharedMemorySegmentBytes = 100 << 10;
@@ skipping 16 matching lines @@
     : bitstream_buffer_id(bbid), timestamp(ts), visible_rect(vr),
       natural_size(ns) {
 }
 
 GpuVideoDecoder::BufferData::~BufferData() {}
 
 GpuVideoDecoder::GpuVideoDecoder(
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
     const scoped_refptr<Factories>& factories)
     : gvd_loop_proxy_(message_loop),
+      weak_factory_(this),
       vda_loop_proxy_(factories->GetMessageLoop()),
       factories_(factories),
       state_(kNormal),
       demuxer_read_in_progress_(false),
       decoder_texture_target_(0),
       next_picture_buffer_id_(0),
       next_bitstream_buffer_id_(0),
       error_occured_(false),
       available_pictures_(-1) {
   DCHECK(factories_);
 }
 
 void GpuVideoDecoder::Reset(const base::Closure& closure)  {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
 
   if (state_ == kDrainingDecoder && !factories_->IsAborted()) {
     gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::Reset, this, closure));
+        &GpuVideoDecoder::Reset, weak_this_, closure));
     // NOTE: if we're deferring Reset() until a Flush() completes, return
     // queued pictures to the VDA so they can be used to finish that Flush().
     if (pending_read_cb_.is_null())
       ready_video_frames_.clear();
     return;
   }
 
   // Throw away any already-decoded, not-yet-delivered frames.
   ready_video_frames_.clear();
 
@@ skipping 23 matching lines @@
   if (!pending_reset_cb_.is_null())
     base::ResetAndReturn(&pending_reset_cb_).Run();
   demuxer_stream_ = NULL;
   BindToCurrentLoop(closure).Run();
 }
 
 void GpuVideoDecoder::Initialize(const scoped_refptr<DemuxerStream>& stream,
                                  const PipelineStatusCB& orig_status_cb,
                                  const StatisticsCB& statistics_cb) {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
+  weak_this_ = weak_factory_.GetWeakPtr();
+
   PipelineStatusCB status_cb = CreateUMAReportingPipelineCB(
       "Media.GpuVideoDecoderInitializeStatus",
       BindToCurrentLoop(orig_status_cb));
   DCHECK(!demuxer_stream_);
 
   if (!stream) {
     status_cb.Run(PIPELINE_ERROR_DECODE);
     return;
   }
 
@@ skipping 17 matching lines @@
     bool os_large_video_support = true;
 #if defined(OS_WIN)
     os_large_video_support = false;
 #endif
     if (!(os_large_video_support && hw_large_video_support)) {
       status_cb.Run(DECODER_ERROR_NOT_SUPPORTED);
       return;
     }
   }
 
+  client_proxy_ = new VDAClientProxy(this);
   VideoDecodeAccelerator* vda =
-      factories_->CreateVideoDecodeAccelerator(config.profile(), this);
+      factories_->CreateVideoDecodeAccelerator(config.profile(), client_proxy_);
   if (!vda) {
     status_cb.Run(DECODER_ERROR_NOT_SUPPORTED);
     return;
   }
 
   if (config.codec() == kCodecH264)
     stream->EnableBitstreamConverter();
 
   demuxer_stream_ = stream;
   statistics_cb_ = statistics_cb;
 
   DVLOG(1) << "GpuVideoDecoder::Initialize() succeeded.";
-  vda_loop_proxy_->PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&GpuVideoDecoder::SetVDA, this, vda),
-      base::Bind(status_cb, PIPELINE_OK));
+  PostTaskAndReplyWithResult(
+      vda_loop_proxy_, FROM_HERE,
+      base::Bind(&VideoDecodeAccelerator::AsWeakPtr, base::Unretained(vda)),
+      base::Bind(&GpuVideoDecoder::SetVDA, weak_this_, status_cb, vda));
 }
 
-void GpuVideoDecoder::SetVDA(VideoDecodeAccelerator* vda) {
-  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+void GpuVideoDecoder::SetVDA(
+    const PipelineStatusCB& status_cb,
+    VideoDecodeAccelerator* vda,
+    base::WeakPtr<VideoDecodeAccelerator> weak_vda) {
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   DCHECK(!vda_.get());
   vda_.reset(vda);
-  weak_vda_ = vda->AsWeakPtr();
+  weak_vda_ = weak_vda;
+  status_cb.Run(PIPELINE_OK);
 }
 
 void GpuVideoDecoder::DestroyTextures() {
   for (std::map<int32, PictureBuffer>::iterator it =
           picture_buffers_in_decoder_.begin();
           it != picture_buffers_in_decoder_.end(); ++it) {
     factories_->DeleteTexture(it->second.texture_id());
   }
   picture_buffers_in_decoder_.clear();
 }
 
+static void DestroyVDAWithClientProxy(
+    const scoped_refptr<VDAClientProxy>& client_proxy,
+    base::WeakPtr<VideoDecodeAccelerator> weak_vda) {
+  DCHECK(client_proxy->HasOneRef());

[xhwang, 2013/04/18 00:40:48]

hmm, are we making assumption about vda implementation details? Can vda just
drop the reference to client_proxy if something bad happened?

Also, can there be a race condition? e.g. can this DCHECK executed before line
325 is executed?

[scherkus (not reviewing), 2013/04/18 18:45:29]

ah good catch -- fischman@ suggested this but you're right that it can race

I don't find it's a very valuable DCHECK - removed

+  if (weak_vda)

[xhwang, 2013/04/18 00:40:48]

OOC, in which case can this happen? DestroyVDA called twice in a row? In that
case shall we check on line 323?

[scherkus (not reviewing), 2013/04/18 18:45:29]

you can only check/deref a weak pointer on the thread it's bound to (hence this
task post)

IIRC fischman@ said it's possible for VDA to get destroyed by other means (e.g.,
compositor)

+    weak_vda->Destroy();

[xhwang, 2013/04/18 00:40:48]

weak_vda.reset()?

[scherkus (not reviewing), 2013/04/18 18:45:29]

Destroy() is a VDA method that takes care of deleting the VDA

.reset() would release a weak reference but leak the VDA object

Did you mean something else?

[xhwang, 2013/04/18 19:17:49]

Sorry, I meant calling .reset() after ->Destroy(). I was worrying about checking
on 312 happens again after 313 is executed (this can happen if DestroyVDA() is
called twice). But since Destroy() deletes the VDA, it should already
invalidates weak_vda_. So no need to call .reset() anymore. 

BTW, does it make sense to call DCHECK(!weak_vda) after 313?

[scherkus (not reviewing), 2013/04/18 20:21:14]

Done.

+}
+
 void GpuVideoDecoder::DestroyVDA() {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
+
+  // |client_proxy| must stay alive until |weak_vda_| has been destroyed.
+  vda_loop_proxy_->PostTask(FROM_HERE, base::Bind(
+      &DestroyVDAWithClientProxy, client_proxy_, weak_vda_));
+
   VideoDecodeAccelerator* vda ALLOW_UNUSED = vda_.release();
-  // Tricky: |this| needs to stay alive until after VDA::Destroy is actually
-  // called, not just posted, so we take an artificial ref to |this| and release
-  // it as |reply| after VDA::Destroy() returns.
-  AddRef();
-  vda_loop_proxy_->PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&VideoDecodeAccelerator::Destroy, weak_vda_),
-      base::Bind(&GpuVideoDecoder::Release, this));
+  client_proxy_->Detach();
+  client_proxy_ = NULL;
 
   DestroyTextures();
 }
 
 void GpuVideoDecoder::Read(const ReadCB& read_cb) {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   DCHECK(pending_reset_cb_.is_null());
   DCHECK(pending_read_cb_.is_null());
   pending_read_cb_ = BindToCurrentLoop(read_cb);
 
@@ skipping 27 matching lines @@
   }
 }
 
 bool GpuVideoDecoder::CanMoreDecodeWorkBeDone() {
   return bitstream_buffers_in_decoder_.size() < kMaxInFlightDecodes;
 }
 
 void GpuVideoDecoder::RequestBufferDecode(
     DemuxerStream::Status status,
     const scoped_refptr<DecoderBuffer>& buffer) {
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   DCHECK_EQ(status != DemuxerStream::kOk, !buffer) << status;
 
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::RequestBufferDecode, this, status, buffer));
-    return;
-  }
   demuxer_read_in_progress_ = false;
 
   if (status != DemuxerStream::kOk) {
     if (pending_read_cb_.is_null())
       return;
 
     // TODO(acolwell): Add support for reinitializing the decoder when
     // |status| == kConfigChanged. For now we just trigger a decode error.
     Status decoder_status =
         (status == DemuxerStream::kAborted) ? kOk : kDecodeError;
@@ skipping 34 matching lines @@
       bitstream_buffer.id(), BufferPair(shm_buffer, buffer))).second;
   DCHECK(inserted);
   RecordBufferData(bitstream_buffer, *buffer);
 
   vda_loop_proxy_->PostTask(FROM_HERE, base::Bind(
       &VideoDecodeAccelerator::Decode, weak_vda_, bitstream_buffer));
 
   if (CanMoreDecodeWorkBeDone()) {
     // Force post here to prevent reentrancy into DemuxerStream.
     gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::EnsureDemuxOrDecode, this));
+        &GpuVideoDecoder::EnsureDemuxOrDecode, weak_this_));
   }
 }
 
 void GpuVideoDecoder::RecordBufferData(
     const BitstreamBuffer& bitstream_buffer, const DecoderBuffer& buffer) {
   input_buffer_data_.push_front(BufferData(
       bitstream_buffer.id(), buffer.GetTimestamp(),
       demuxer_stream_->video_decoder_config().visible_rect(),
       demuxer_stream_->video_decoder_config().natural_size()));
   // Why this value?  Because why not.  avformat.h:MAX_REORDER_DELAY is 16, but
@@ skipping 32 matching lines @@
   return available_pictures_ > 0;
 }
 
 void GpuVideoDecoder::NotifyInitializeDone() {
   NOTREACHED() << "GpuVideoDecodeAcceleratorHost::Initialize is synchronous!";
 }
 
 void GpuVideoDecoder::ProvidePictureBuffers(uint32 count,
                                             const gfx::Size& size,
                                             uint32 texture_target) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::ProvidePictureBuffers, this, count, size,
-        texture_target));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
 
   std::vector<uint32> texture_ids;
   decoder_texture_target_ = texture_target;
   if (!factories_->CreateTextures(
       count, size, &texture_ids, decoder_texture_target_)) {
     NotifyError(VideoDecodeAccelerator::PLATFORM_FAILURE);
     return;
   }
 
   if (!vda_.get())
     return;
 
   CHECK_EQ(available_pictures_, -1);
   available_pictures_ = count;
 
   std::vector<PictureBuffer> picture_buffers;
   for (size_t i = 0; i < texture_ids.size(); ++i) {
     picture_buffers.push_back(PictureBuffer(
         next_picture_buffer_id_++, size, texture_ids[i]));
     bool inserted = picture_buffers_in_decoder_.insert(std::make_pair(
         picture_buffers.back().id(), picture_buffers.back())).second;
     DCHECK(inserted);
   }
   vda_loop_proxy_->PostTask(FROM_HERE, base::Bind(
       &VideoDecodeAccelerator::AssignPictureBuffers, weak_vda_,
       picture_buffers));
 }
 
 void GpuVideoDecoder::DismissPictureBuffer(int32 id) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::DismissPictureBuffer, this, id));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
+
   std::map<int32, PictureBuffer>::iterator it =
       picture_buffers_in_decoder_.find(id);
   if (it == picture_buffers_in_decoder_.end()) {
     NOTREACHED() << "Missing picture buffer: " << id;
     return;
   }
   factories_->DeleteTexture(it->second.texture_id());
   picture_buffers_in_decoder_.erase(it);
 }
 
 void GpuVideoDecoder::PictureReady(const media::Picture& picture) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::PictureReady, this, picture));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
+
   std::map<int32, PictureBuffer>::iterator it =
       picture_buffers_in_decoder_.find(picture.picture_buffer_id());
   if (it == picture_buffers_in_decoder_.end()) {
     NOTREACHED() << "Missing picture buffer: " << picture.picture_buffer_id();
     NotifyError(VideoDecodeAccelerator::PLATFORM_FAILURE);
     return;
   }
   const PictureBuffer& pb = it->second;
 
   // Update frame's timestamp.
   base::TimeDelta timestamp;
   gfx::Rect visible_rect;
   gfx::Size natural_size;
   GetBufferData(picture.bitstream_buffer_id(), &timestamp, &visible_rect,
                 &natural_size);
   DCHECK(decoder_texture_target_);
   scoped_refptr<VideoFrame> frame(
       VideoFrame::WrapNativeTexture(
           pb.texture_id(), decoder_texture_target_, pb.size(), visible_rect,
           natural_size, timestamp,
           base::Bind(&Factories::ReadPixels, factories_, pb.texture_id(),
                      decoder_texture_target_,
                      gfx::Size(visible_rect.width(), visible_rect.height())),
-          base::Bind(&GpuVideoDecoder::ReusePictureBuffer, this,
-                     picture.picture_buffer_id())));
+          BindToCurrentLoop(base::Bind(
+              &GpuVideoDecoder::ReusePictureBuffer, weak_this_,
+              picture.picture_buffer_id()))));
   CHECK_GT(available_pictures_, 0);
   available_pictures_--;
 
   EnqueueFrameAndTriggerFrameDelivery(frame);
 }
 
 void GpuVideoDecoder::EnqueueFrameAndTriggerFrameDelivery(
     const scoped_refptr<VideoFrame>& frame) {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
 
   // During a pending vda->Reset(), we don't accumulate frames.  Drop it on the
   // floor and return.
   if (!pending_reset_cb_.is_null())
     return;
 
   if (frame)
     ready_video_frames_.push_back(frame);
   else
     DCHECK(!ready_video_frames_.empty());
 
   if (pending_read_cb_.is_null())
     return;
 
   base::ResetAndReturn(&pending_read_cb_).Run(kOk, ready_video_frames_.front());
   ready_video_frames_.pop_front();
 }
 
 void GpuVideoDecoder::ReusePictureBuffer(int64 picture_buffer_id) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::ReusePictureBuffer, this, picture_buffer_id));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   CHECK_GE(available_pictures_, 0);
   available_pictures_++;
 
   if (!vda_.get())
     return;
   vda_loop_proxy_->PostTask(FROM_HERE, base::Bind(
       &VideoDecodeAccelerator::ReusePictureBuffer, weak_vda_,
       picture_buffer_id));
 }
 
@@ skipping 12 matching lines @@
   available_shm_segments_.pop_back();
   return ret;
 }
 
 void GpuVideoDecoder::PutSHM(SHMBuffer* shm_buffer) {
   DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   available_shm_segments_.push_back(shm_buffer);
 }
 
 void GpuVideoDecoder::NotifyEndOfBitstreamBuffer(int32 id) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::NotifyEndOfBitstreamBuffer, this, id));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
 
   std::map<int32, BufferPair>::iterator it =
       bitstream_buffers_in_decoder_.find(id);
   if (it == bitstream_buffers_in_decoder_.end()) {
     NotifyError(VideoDecodeAccelerator::PLATFORM_FAILURE);
     NOTREACHED() << "Missing bitstream buffer: " << id;
     return;
   }
 
   PutSHM(it->second.shm_buffer);
@@ skipping 34 matching lines @@
 
   // The second condition can happen during the tear-down process.
   // GpuVideoDecoder::Stop() returns the |pending_read_cb_| immediately without
   // waiting for the demuxer read to be returned. Therefore, this function could
   // be called even after the decoder has been stopped.
   if (demuxer_read_in_progress_ || !demuxer_stream_)
     return;
 
   demuxer_read_in_progress_ = true;
   demuxer_stream_->Read(base::Bind(
-      &GpuVideoDecoder::RequestBufferDecode, this));
+      &GpuVideoDecoder::RequestBufferDecode, weak_this_));
 }
 
 void GpuVideoDecoder::NotifyFlushDone() {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::NotifyFlushDone, this));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   DCHECK_EQ(state_, kDrainingDecoder);
   state_ = kDecoderDrained;
   EnqueueFrameAndTriggerFrameDelivery(VideoFrame::CreateEmptyFrame());
 }
 
 void GpuVideoDecoder::NotifyResetDone() {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::NotifyResetDone, this));
-    return;
-  }
-
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   DCHECK(ready_video_frames_.empty());
 
   // This needs to happen after the Reset() on vda_ is done to ensure pictures
   // delivered during the reset can find their time data.
   input_buffer_data_.clear();
 
   if (!pending_reset_cb_.is_null())
     base::ResetAndReturn(&pending_reset_cb_).Run();
 
   if (!pending_read_cb_.is_null())
     EnqueueFrameAndTriggerFrameDelivery(VideoFrame::CreateEmptyFrame());
 }
 
 void GpuVideoDecoder::NotifyError(media::VideoDecodeAccelerator::Error error) {
-  if (!gvd_loop_proxy_->BelongsToCurrentThread()) {
-    gvd_loop_proxy_->PostTask(FROM_HERE, base::Bind(
-        &GpuVideoDecoder::NotifyError, this, error));
-    return;
-  }
+  DCHECK(gvd_loop_proxy_->BelongsToCurrentThread());
   if (!vda_.get())
     return;
 
   DLOG(ERROR) << "VDA Error: " << error;
   DestroyVDA();
 
   error_occured_ = true;
 
   if (!pending_read_cb_.is_null()) {
     base::ResetAndReturn(&pending_read_cb_).Run(kDecodeError, NULL);
     return;
   }
 }
 
 }  // namespace media