Initial support for native accessibility in ARC

components/exo/surface_observer.h

 // Copyright 2015 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 COMPONENTS_EXO_SURFACE_OBSERVER_H_
 #define COMPONENTS_EXO_SURFACE_OBSERVER_H_
 
+#include <stdint.h>
+
 namespace exo {
 class Surface;
 
 // Observers can listen to various events on the Surfaces.
 class SurfaceObserver {
  public:
   // Called at the top of the surface's destructor, to give observers a
   // chance to remove themselves.
   virtual void OnSurfaceDestroying(Surface* surface) = 0;
 
+  // Called when a surface has an accessibility tree attached or detached.
+  virtual void OnSurfaceAXTreeChanged(int32_t id) {}
+
  protected:
   virtual ~SurfaceObserver() {}
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_SURFACE_OBSERVER_H_