content: Remove gpu memory buffer manager from ChildThreadImpl.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 4f2d0bcc84f67cb9a89abf748eb893ce4f65fea5..fff45f3220ab532a741c2fcc899eecb86c3493aa 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -105,6 +105,7 @@ class AudioRendererMixerManager;
 class BlobMessageFilter;
 class BrowserPluginManager;
 class CacheStorageDispatcher;
+class ChildGpuMemoryBufferManager;
 class CompositorForwardingMessageFilter;
 class ContextProviderCommandBuffer;
 class DBMessageFilter;
@@ -634,6 +635,8 @@ class CONTENT_EXPORT RenderThreadImpl
   // May be null if overridden by ContentRendererClient.
   std::unique_ptr<blink::scheduler::WebThreadBase> compositor_thread_;
 
+  std::unique_ptr<ChildGpuMemoryBufferManager> gpu_memory_buffer_manager_;
+
   // Utility class to provide GPU functionalities to media.
   // TODO(dcastagna): This should be just one scoped_ptr once
   // http://crbug.com/580386 is fixed.