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

ui/ozone/public/gpu_platform_support.h

+// 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.
+
+#ifndef UI_OZONE_PUBLIC_GPU_PLATFORM_SUPPORT_H_
+#define UI_OZONE_PUBLIC_GPU_PLATFORM_SUPPORT_H_
+
+#include "ipc/ipc_listener.h"
+#include "ipc/ipc_sender.h"
+#include "ui/ozone/ozone_base_export.h"
+
+namespace ui {
+
+// Platform-specific object to support a GPU process.
+//
+// See GpuPlatformSupportHost for more context.
+class OZONE_BASE_EXPORT GpuPlatformSupport : public IPC::Listener {
+ public:
+  GpuPlatformSupport();
+  virtual ~GpuPlatformSupport();
+
+  // Called when the GPU process is spun up & channel established.
+  virtual void OnChannelEstablished(IPC::Sender* sender) = 0;
+};
+
+// Create a stub implementation.
+OZONE_BASE_EXPORT GpuPlatformSupport* CreateStubGpuPlatformSupport();
+
+}  // namespace ui
+
+#endif  // UI_OZONE_PUBLIC_GPU_PLATFORM_SUPPORT_H_