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

services/ui/public/cpp/gles2_context.cc

Index: services/ui/public/cpp/gles2_context.cc
diff --git a/services/ui/public/cpp/gles2_context.cc b/services/ui/public/cpp/gles2_context.cc
index 4d4dec8ac62b46cab0597d24ca44aaac56ac3822..718951a0b55452b6ee20bd4146508f97fbff469d 100644
--- a/services/ui/public/cpp/gles2_context.cc
+++ b/services/ui/public/cpp/gles2_context.cc
@@ -25,11 +25,9 @@ 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;
@@ -76,9 +74,11 @@ bool GLES2Context::Initialize(GpuService* gpu_service) {
 
 // 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;
 }