Fix lifecycle-vs-threads of GpuVDAContext3D.

content/renderer/media/renderer_gpu_video_decoder_factories.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 "content/renderer/media/renderer_gpu_video_decoder_factories.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 
 #include "base/bind.h"
 #include "base/synchronization/waitable_event.h"
 #include "content/common/child_thread.h"
 #include "content/common/gpu/client/gpu_channel_host.h"
 #include "content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
 #include "gpu/ipc/command_buffer_proxy.h"
 
 RendererGpuVideoDecoderFactories::~RendererGpuVideoDecoderFactories() {}
 RendererGpuVideoDecoderFactories::RendererGpuVideoDecoderFactories(
     GpuChannelHost* gpu_channel_host,
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
-    const base::WeakPtr<WebGraphicsContext3DCommandBufferImpl>& context)
+    WebGraphicsContext3DCommandBufferImpl* context)
     : message_loop_(message_loop),
-      gpu_channel_host_(gpu_channel_host),
-      context_(context) {
-  DCHECK(context_);
-  context_->DetachFromThread();
+      gpu_channel_host_(gpu_channel_host) {
   if (message_loop_->BelongsToCurrentThread()) {
-    AsyncGetContext(NULL);
+    AsyncGetContext(context, NULL);
     return;
   }
   // Threaded compositor requires us to wait for the context to be acquired.
   base::WaitableEvent waiter(false, false);
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &RendererGpuVideoDecoderFactories::AsyncGetContext,
       // Unretained to avoid ref/deref'ing |*this|, which is not yet stored in a
       // scoped_refptr.  Safe because the Wait() below keeps us alive until this
       // task completes.
-      base::Unretained(this), &waiter));
+      base::Unretained(this),
+      // OK to pass raw because the pointee is only deleted on the compositor
+      // thread, and only as the result of a PostTask from the render thread
+      // which can only happen after this function returns, so our PostTask will
+      // run first.
+      context,
+      &waiter));
   waiter.Wait();
 }
 
 void RendererGpuVideoDecoderFactories::AsyncGetContext(
+    WebGraphicsContext3DCommandBufferImpl* context,
     base::WaitableEvent* waiter) {
+  context_ = context->AsWeakPtr();
   if (context_)
     context_->makeContextCurrent();
   if (waiter)
     waiter->Signal();
 }
 
 media::VideoDecodeAccelerator*
 RendererGpuVideoDecoderFactories::CreateVideoDecodeAccelerator(
     media::VideoCodecProfile profile,
     media::VideoDecodeAccelerator::Client* client) {
@@ skipping 98 matching lines @@
   waiter.Wait();
   return shm;
 }
 
 void RendererGpuVideoDecoderFactories::AsyncCreateSharedMemory(
     size_t size, base::SharedMemory** shm, base::WaitableEvent* waiter) {
   DCHECK_EQ(MessageLoop::current(), ChildThread::current()->message_loop());
   *shm = ChildThread::current()->AllocateSharedMemory(size);
   waiter->Signal();
 }