gpu: Add GpuFence framework.

content/child/child_gpu_memory_buffer_manager.h

Index: content/child/child_gpu_memory_buffer_manager.h
diff --git a/content/child/child_gpu_memory_buffer_manager.h b/content/child/child_gpu_memory_buffer_manager.h
index fcd7c486cdea0cf88ad48782cb9d8147005870f4..64e81206a3d3c4ad0dda66ec4029550e73e6a16d 100644
--- a/content/child/child_gpu_memory_buffer_manager.h
+++ b/content/child/child_gpu_memory_buffer_manager.h
@@ -30,6 +30,10 @@ class ChildGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager {
       gfx::BufferFormat format) override;
   void SetDestructionSyncToken(gfx::GpuMemoryBuffer* buffer,
                                const gpu::SyncToken& sync_token) override;
+  std::unique_ptr<gfx::GpuFence> CreateGpuFence() override;
+  std::unique_ptr<gfx::GpuFence> CreateGpuFenceFromHandle(
+      const gfx::GpuFenceHandle& handle) override;
+  gfx::GpuFence* GpuFenceFromClientFence(ClientFence fence) override;
 
  private:
   scoped_refptr<ThreadSafeSender> sender_;