[Ozone-DRI] Assume window IPC arrives before surface IPC

ui/ozone/platform/dri/dri_window.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_PLATFORM_DRI_DRI_WINDOW_H_
 #define UI_OZONE_PLATFORM_DRI_DRI_WINDOW_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/display/types/display_snapshot.h"
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/dri/channel_observer.h"
 #include "ui/platform_window/platform_window.h"
 
 namespace ui {
 
 class DisplayManager;
 class DriCursor;
 class DriWindowDelegate;
 class DriWindowManager;
 class EventFactoryEvdev;
 class DriGpuPlatformSupportHost;
 
+// Implementation of the platform window. This object and its handle |widget_|
+// uniquely identify a window. Since the DRI/GBM platform is split into 2
+// pieces (Browser process and GPU process), internally we need to make sure the
+// state is synchronized between the 2 processes.
+//
+// |widget_| is used in both processes to uniquely identify the window. This
+// means that any state on the browser side needs to be propagated to the GPU.
+// State propagation needs to happen before the state change is acknowledged to
+// |delegate_| as |delegate_| is responsible for initializing the surface
+// associated with the window (the surface is created on the GPU process).
 class DriWindow : public PlatformWindow,
                   public PlatformEventDispatcher,
                   public ChannelObserver {
  public:
   DriWindow(PlatformWindowDelegate* delegate,
             const gfx::Rect& bounds,
             DriGpuPlatformSupportHost* sender,
             EventFactoryEvdev* event_factory,
             DriCursor* cursor,
             DriWindowManager* window_manager,
@@ skipping 39 matching lines @@
 
   gfx::Rect bounds_;
   gfx::AcceleratedWidget widget_;
 
   DISALLOW_COPY_AND_ASSIGN(DriWindow);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRI_DRI_WINDOW_H_