gpu: Add GpuFence framework.

services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h

Index: services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h
diff --git a/services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h b/services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h
index 1346ff584a046bf9bf9851ea1a7447a9e3b912db..f60866a9d03039f78fc413ed1c7d77d3d8ea3176 100644
--- a/services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h
+++ b/services/ui/public/cpp/mojo_gpu_memory_buffer_manager.h
@@ -57,6 +57,11 @@ 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;
+
   int counter_ = 0;
   // TODO(sad): Explore the option of doing this from an existing thread.
   base::Thread thread_;