Add an adapter layer (WMHelper) between exo and ash.

components/exo/keyboard.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_KEYBOARD_H_
 #define COMPONENTS_EXO_KEYBOARD_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "components/exo/surface_observer.h"
+#include "components/exo/wm_helper.h"
 #include "ui/aura/client/focus_change_observer.h"
 #include "ui/events/event_handler.h"
 
 namespace ui {
 enum class DomCode;
 class Event;
 class KeyEvent;
 }
 
 namespace exo {
 class KeyboardDelegate;
 class Surface;
 
 // This class implements a client keyboard that represents one or more keyboard
 // devices.
 class Keyboard : public ui::EventHandler,
-                 public aura::client::FocusChangeObserver,
+                 public WMHelper::FocusObserver,
                  public SurfaceObserver {
  public:
   explicit Keyboard(KeyboardDelegate* delegate);
   ~Keyboard() override;
 
   // Overridden from ui::EventHandler:
   void OnKeyEvent(ui::KeyEvent* event) override;
 
-  // Overridden aura::client::FocusChangeObserver:
+  // Overridden WMHelper::FocusObserver:
   void OnWindowFocused(aura::Window* gained_focus,
                        aura::Window* lost_focus) override;
 
   // Overridden from SurfaceObserver:
   void OnSurfaceDestroying(Surface* surface) override;
 
  private:
   // Returns the effective focus for |window|.
   Surface* GetEffectiveFocus(aura::Window* window) const;
 
   // The delegate instance that all events are dispatched to.
   KeyboardDelegate* const delegate_;
 
   // The current focus surface for the keyboard.
   Surface* focus_ = nullptr;
 
   // Vector of currently pressed keys.
   std::vector<ui::DomCode> pressed_keys_;
 
   // Current set of modifier flags.
   int modifier_flags_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(Keyboard);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_KEYBOARD_H_