services/ui: Use a gpu::GpuChannelHost when creating ui::OutputSurface.

services/ui/public/cpp/gles2_context.cc

 // Copyright 2014 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.
 
 #include "services/ui/public/cpp/gles2_context.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
 
 #include "gpu/command_buffer/client/gles2_cmd_helper.h"
 #include "gpu/command_buffer/client/shared_memory_limits.h"
 #include "gpu/command_buffer/client/transfer_buffer.h"
 #include "gpu/ipc/client/command_buffer_proxy_impl.h"
 #include "gpu/ipc/client/gpu_channel_host.h"
 #include "mojo/public/cpp/system/core.h"
 #include "services/ui/public/cpp/gpu_service.h"
 #include "services/ui/public/interfaces/gpu_service.mojom.h"
 #include "url/gurl.h"
 
 namespace ui {
 
 GLES2Context::GLES2Context() {}
 
 GLES2Context::~GLES2Context() {}
 
-bool GLES2Context::Initialize(GpuService* gpu_service) {
-  scoped_refptr<gpu::GpuChannelHost> gpu_channel_host =
-      gpu_service->EstablishGpuChannelSync();
-  if (!gpu_channel_host)
-    return false;
+bool GLES2Context::Initialize(
+    scoped_refptr<gpu::GpuChannelHost> gpu_channel_host) {
+  DCHECK(gpu_channel_host);
   gpu::SurfaceHandle surface_handle = gfx::kNullAcceleratedWidget;
   // TODO(penghuang): support shared group.
   gpu::CommandBufferProxyImpl* shared_command_buffer = nullptr;
   gpu::GpuStreamId stream_id = gpu::GpuStreamId::GPU_STREAM_DEFAULT;
   gpu::GpuStreamPriority stream_priority = gpu::GpuStreamPriority::NORMAL;
   gpu::gles2::ContextCreationAttribHelper attributes;
   // TODO(penghuang): figure a useful active_url.
   GURL active_url;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       base::ThreadTaskRunnerHandle::Get();
@@ skipping 26 matching lines @@
   if (!implementation_->Initialize(default_limits.start_transfer_buffer_size,
                                    default_limits.min_transfer_buffer_size,
                                    default_limits.max_transfer_buffer_size,
                                    default_limits.mapped_memory_reclaim_limit))
     return false;
   return true;
 }
 
 // static
 std::unique_ptr<GLES2Context> GLES2Context::CreateOffscreenContext(
-    GpuService* gpu_service) {
+    scoped_refptr<gpu::GpuChannelHost> gpu_channel_host) {
+  if (!gpu_channel_host)
+    return nullptr;
   std::unique_ptr<GLES2Context> gles2_context(new GLES2Context);

[sky, 2016/08/18 13:15:45]

This section is subtle and worth a comment. For example, why not create the
context if initialize succeeds?

[sadrul, 2016/08/18 14:59:48]

We keep the context if it was successfully initialized, and destroy it if it
wasn't initialized due to some error.

[sky, 2016/08/18 19:12:09]

Makes sense, please add a comment to the code as well.

[sadrul, 2016/08/18 20:53:28]

Done.

-  if (!gles2_context->Initialize(gpu_service))
+  if (!gles2_context->Initialize(std::move(gpu_channel_host)))
     gles2_context.reset();
   return gles2_context;
 }
 
 }  // namespace ui