ARC: Avoid duplicate observers in IME service

components/arc/ime/arc_ime_service.h

 // Copyright 2016 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_ARC_IME_ARC_IME_SERVICE_H_
 #define COMPONENTS_ARC_IME_ARC_IME_SERVICE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "components/arc/arc_service.h"
 #include "components/arc/ime/arc_ime_bridge.h"
 #include "ui/aura/client/focus_change_observer.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/ime/text_input_flags.h"
 #include "ui/base/ime/text_input_type.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/keyboard/keyboard_controller.h"
 #include "ui/keyboard/keyboard_controller_observer.h"
 
 namespace aura {
+namespace client {
+class FocusClient;
+}
+
 class Window;
 }
 
 namespace ui {
 class InputMethod;
 }
 
 namespace arc {
 
 class ArcBridgeService;
@@ skipping 72 matching lines @@
   }
 
  private:
   ui::InputMethod* GetInputMethod();
 
   std::unique_ptr<ArcImeBridge> ime_bridge_;
   ui::TextInputType ime_type_;
   gfx::Rect cursor_rect_;
   bool has_composition_text_;
 
-  aura::WindowTracker observing_root_windows_;
   aura::WindowTracker arc_windows_;
   aura::WindowTracker focused_arc_window_;
 
+  aura::client::FocusClient* focus_client_;
   keyboard::KeyboardController* keyboard_controller_;
 
   ui::InputMethod* test_input_method_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcImeService);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_IME_ARC_IME_SERVICE_H_