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

ui/ozone/gpu/gpu_platform_support_host.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_host.h"
+
+#include "base/debug/trace_event.h"
+#include "base/logging.h"
+#include "ui/ozone/ozone_export.h"
+
+namespace ui {
+
+namespace {
+
+// No-op implementations of GpuPlatformSupportHost.
+class OZONE_EXPORT StubGpuPlatformSupportHost
+    : public GpuPlatformSupportHost {
+ public:
+  // GpuPlatformSupportHost:
+  virtual void OnChannelEstablished(int host_id, IPC::Sender* sender) OVERRIDE {
+  }
+  virtual void OnChannelDestroyed(int host_id) OVERRIDE {}
+  virtual bool OnMessageReceived(const IPC::Message&) OVERRIDE { return false; }
+};
+
+}  // namespace
+
+GpuPlatformSupportHost::GpuPlatformSupportHost() {
+  DCHECK(!instance_);
+  instance_ = this;
+}
+
+GpuPlatformSupportHost::~GpuPlatformSupportHost() {
+  DCHECK(instance_ == this);
+  instance_ = NULL;
+}
+
+// static
+GpuPlatformSupportHost* GpuPlatformSupportHost::GetInstance() {
+  return instance_;
+}
+
+// static
+GpuPlatformSupportHost* GpuPlatformSupportHost::instance_;
+
+GpuPlatformSupportHost* CreateStubGpuPlatformSupportHost() {
+  return new StubGpuPlatformSupportHost;
+}
+
+}  // namespace ui