Post GpuMemoryBufferVideoFramePool deletion on media thread

media/video/gpu_memory_buffer_video_frame_pool.cc

Index: media/video/gpu_memory_buffer_video_frame_pool.cc
diff --git a/media/video/gpu_memory_buffer_video_frame_pool.cc b/media/video/gpu_memory_buffer_video_frame_pool.cc
index 7ac0cd763324765bc657812752e301031e5e0d7a..68f2537007a9c583fd27d375889ad8ee7fc77d9b 100644
--- a/media/video/gpu_memory_buffer_video_frame_pool.cc
+++ b/media/video/gpu_memory_buffer_video_frame_pool.cc
@@ -757,14 +757,16 @@ void GpuMemoryBufferVideoFramePool::PoolImpl::ReturnFrameResources(
   frame_resources->SetIsInUse(false);
 }
 
-GpuMemoryBufferVideoFramePool::GpuMemoryBufferVideoFramePool() {}
+GpuMemoryBufferVideoFramePool::GpuMemoryBufferVideoFramePool()
+    : weak_ptr_factory_(this) {}
 
 GpuMemoryBufferVideoFramePool::GpuMemoryBufferVideoFramePool(
     const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
     const scoped_refptr<base::TaskRunner>& worker_task_runner,
     GpuVideoAcceleratorFactories* gpu_factories)
     : pool_impl_(
-          new PoolImpl(media_task_runner, worker_task_runner, gpu_factories)) {
+          new PoolImpl(media_task_runner, worker_task_runner, gpu_factories)),
+      weak_ptr_factory_(this) {
   base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       pool_impl_.get(), "GpuMemoryBufferVideoFramePool", media_task_runner);
 }
@@ -781,4 +783,9 @@ void GpuMemoryBufferVideoFramePool::MaybeCreateHardwareFrame(
   pool_impl_->CreateHardwareFrame(video_frame, frame_ready_cb);
 }
 
+base::WeakPtr<GpuMemoryBufferVideoFramePool>
+GpuMemoryBufferVideoFramePool::GetWeakPtr() {
+  return weak_ptr_factory_.GetWeakPtr();
+}
+
 }  // namespace media