mus: Use ui::ContextProviderCommandBuffer.

services/ui/public/cpp/gpu/gpu.h

Index: services/ui/public/cpp/gpu/gpu.h
diff --git a/services/ui/public/cpp/gpu/gpu.h b/services/ui/public/cpp/gpu/gpu.h
index c8386681209e603827a29f5f3f0b79365fed6484..f99250a65d4376a258ead4a999646095ac263d7b 100644
--- a/services/ui/public/cpp/gpu/gpu.h
+++ b/services/ui/public/cpp/gpu/gpu.h
@@ -13,6 +13,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
+#include "cc/output/context_provider.h"
 #include "gpu/ipc/client/gpu_channel_host.h"
 #include "services/ui/public/cpp/gpu/client_gpu_memory_buffer_manager.h"
 #include "services/ui/public/interfaces/gpu.mojom.h"
@@ -43,6 +44,9 @@ class Gpu : public gpu::GpuChannelHostFactory,
       service_manager::InterfaceProvider*,
       scoped_refptr<base::SingleThreadTaskRunner> task_runner = nullptr);
 
+  scoped_refptr<cc::ContextProvider> CreateContextProvider(
+      scoped_refptr<gpu::GpuChannelHost> gpu_channel);
+
   // gpu::GpuChannelEstablishFactory:
   void EstablishGpuChannel(
       const gpu::GpuChannelEstablishedCallback& callback) override;
@@ -57,7 +61,6 @@ class Gpu : public gpu::GpuChannelHostFactory,
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
 
   scoped_refptr<gpu::GpuChannelHost> GetGpuChannel();
-  void EstablishGpuChannelOnMainThreadSyncLocked();
   void OnEstablishedGpuChannel(int client_id,
                                mojo::ScopedMessagePipeHandle channel_handle,
                                const gpu::GPUInfo& gpu_info);