Mus: Implement GpuMain mojo interface

services/ui/gpu/interfaces/gpu_service_internal.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module ui.mojom;
 
 import "cc/ipc/display_compositor.mojom";
 import "gpu/ipc/common/gpu_info.mojom";
 import "gpu/ipc/common/surface_handle.mojom";
 import "gpu/ipc/common/sync_token.mojom";
@@ skipping 15 matching lines @@
                         gfx.mojom.Size size,
                         gfx.mojom.BufferFormat format,
                         gfx.mojom.BufferUsage usage,
                         int32 client_id,
                         gpu.mojom.SurfaceHandle surface_handle)
       => (gfx.mojom.GpuMemoryBufferHandle buffer_handle);
 
   DestroyGpuMemoryBuffer(gfx.mojom.GpuMemoryBufferId id,
                          int32 client_id,
                          gpu.mojom.SyncToken sync_token);
-
-  // Tells the GPU process to create a display compositor.
-  CreateDisplayCompositor(
-    cc.mojom.DisplayCompositor& display_compositor,
-    cc.mojom.DisplayCompositorClient display_compositor_client);
 };