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

ui/ozone/gpu/gpu_platform_support_host.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_GPU_GPU_PLATFORM_SUPPORT_HOST_H_
+#define UI_OZONE_GPU_GPU_PLATFORM_SUPPORT_HOST_H_
+
+#include "ipc/ipc_listener.h"
+#include "ipc/ipc_sender.h"
+#include "ui/ozone/gpu/ozone_gpu_export.h"
+
+namespace ui {
+
+// Conduit for display-related messaging from browser to GPU (browser end).
+//
+// ChromeOS on bare hardware will do display configuration and cursor
+// movement from the GPU process. This is the conduit for the messages
+// needed to make this work.
+//
+// Under X11, we don't need any GPU messages for display configuration.
+// That's why there's no real functionality here: it's purely mechanism
+// to support additional messages needed by specific platforms.

[rjkroege, 2014/06/18 17:02:25]

I think it would be really nice to add a little example of how this should be
used. In particular, the calling sequence that we would expect and what are the
expectations on a platform that needs this functionality.

[spang, 2014/06/18 23:21:42]

The display configuration bits will provide an example. I think that probably
fills this need.

+class OZONE_GPU_EXPORT GpuPlatformSupportHost : public IPC::Listener {
+ public:
+  virtual ~GpuPlatformSupportHost() {}
+
+  // Initialize the static instance.
+  static GpuPlatformSupportHost* Initialize();
+
+  // Get the static instance.
+  static GpuPlatformSupportHost* GetInstance();
+
+  // Called when the GPU process is spun up & channel established.
+  virtual void OnChannelEstablished(int host_id, IPC::Sender* sender) = 0;
+  // Called when the GPU process is destroyed.
+  virtual void OnChannelDestroyed(int host_id) = 0;
+
+ private:
+  static GpuPlatformSupportHost* instance_;
+};
+
+// create a stub implementation.
+OZONE_GPU_EXPORT GpuPlatformSupportHost* CreateStubGpuPlatformSupportHost();
+
+}  // namespace ui
+
+#endif  // UI_OZONE_GPU_GPU_PLATFORM_SUPPORT_HOST_H_