ozone: Add overlay candidate implementation that queries support via IPC

ui/ozone/public/overlay_manager_ozone.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 UI_OZONE_PUBLIC_OVERLAY_MANAGER_OZONE_H_
 #define UI_OZONE_PUBLIC_OVERLAY_MANAGER_OZONE_H_
 
+#include "base/memory/scoped_ptr.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace ui {
 
 class OverlayCandidatesOzone;
 
 // Responsible for providing the oracles used to decide when overlays can be
 // used.
 class OverlayManagerOzone {
  public:
   virtual ~OverlayManagerOzone() {}
 
   // Get the hal struct to check for overlay support.
-  virtual OverlayCandidatesOzone* GetOverlayCandidates(
+  virtual scoped_ptr<OverlayCandidatesOzone> GetOverlayCandidates(
       gfx::AcceleratedWidget w) = 0;
 
   // Returns true if overlays can be shown at z-index 0, replacing the main
   // surface. Combined with surfaceless extensions, it allows for an
   // overlay-only mode.
   virtual bool CanShowPrimaryPlaneAsOverlay() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PUBLIC_OVERLAY_MANAGER_OZONE_H_