gpu: Add GpuFence framework.

ui/aura/mus/mojo_gpu_memory_buffer_manager.h

Index: ui/aura/mus/mojo_gpu_memory_buffer_manager.h
diff --git a/ui/aura/mus/mojo_gpu_memory_buffer_manager.h b/ui/aura/mus/mojo_gpu_memory_buffer_manager.h
index a5c35760a7aa40428ab4f50bf0435430ad42933a..eb83c66b6d9bf3bad28e2126318dbe1ecb82017c 100644
--- a/ui/aura/mus/mojo_gpu_memory_buffer_manager.h
+++ b/ui/aura/mus/mojo_gpu_memory_buffer_manager.h
@@ -29,6 +29,10 @@ class MojoGpuMemoryBufferManager : 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:
   DISALLOW_COPY_AND_ASSIGN(MojoGpuMemoryBufferManager);