gpu: Add GpuFence framework.

cc/test/test_gpu_memory_buffer_manager.h

Index: cc/test/test_gpu_memory_buffer_manager.h
diff --git a/cc/test/test_gpu_memory_buffer_manager.h b/cc/test/test_gpu_memory_buffer_manager.h
index 59524b15dbfd89745263cd609c201e19845dd203..0a994391e2ee557da5b6e191244bf4fe3cdb0eb2 100644
--- a/cc/test/test_gpu_memory_buffer_manager.h
+++ b/cc/test/test_gpu_memory_buffer_manager.h
@@ -35,6 +35,10 @@ class TestGpuMemoryBufferManager : 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:
   // Buffers allocated by this manager.