ozone: gpu: Add plumbing for platform-specific gpu messaging

ui/ozone/gpu/gpu_platform_support.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 "ui/ozone/gpu/gpu_platform_support.h"
+
+#include "base/logging.h"
+#include "ui/ozone/ozone_export.h"
+
+namespace ui {
+
+namespace {
+
+// No-op implementation of GpuPlatformSupport.
+class OZONE_EXPORT StubGpuPlatformSupport : public GpuPlatformSupport {
+ public:
+  // GpuPlatformSupport:
+  virtual void OnChannelEstablished(IPC::Sender* sender) {}
+  bool OnMessageReceived(const IPC::Message&) OVERRIDE { return false; }
+};
+
+}  // namespace
+
+GpuPlatformSupport::GpuPlatformSupport() {
+  DCHECK(!instance_);
+  instance_ = this;
+}
+
+GpuPlatformSupport::~GpuPlatformSupport() {
+  DCHECK(instance_ == this);
+  instance_ = NULL;
+}
+
+// static
+GpuPlatformSupport* GpuPlatformSupport::GetInstance() {
+  return instance_;
+}
+
+// static
+GpuPlatformSupport* GpuPlatformSupport::instance_;
+
+GpuPlatformSupport* CreateStubGpuPlatformSupport() {
+  return new StubGpuPlatformSupport;
+}
+
+}  // namespace ui