Converts focusmanager from delegate to observer

components/mus/ws/focus_controller.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_MUS_WS_FOCUS_CONTROLLER_H_
 #define COMPONENTS_MUS_WS_FOCUS_CONTROLLER_H_
 
 #include "base/memory/scoped_ptr.h"
+#include "base/observer_list.h"
 #include "components/mus/ws/server_window_drawn_tracker_observer.h"
 
 namespace mus {
 
 namespace ws {
 
-class FocusControllerDelegate;
+class FocusControllerObserver;
 class ServerWindow;
 class ServerWindowDrawnTracker;
 
-// Tracks a focused window. Focus is moved to another window when the drawn
-// state of the focused window changes and the delegate is notified.
+// Describes the source of the change.
+enum class FocusControllerChangeSource {
+  EXPLICIT,
+  DRAWN_STATE_CHANGED,
+};
+
+// Tracks the focused window. Focus is moved to another window when the drawn
+// state of the focused window changes.
 class FocusController : public ServerWindowDrawnTrackerObserver {
  public:
-  explicit FocusController(FocusControllerDelegate* delegate);
+  FocusController();
   ~FocusController() override;
 
   // Sets the focused window. Does nothing if |window| is currently focused.
   // This does not notify the delegate.
   void SetFocusedWindow(ServerWindow* window);
   ServerWindow* GetFocusedWindow();
 
   // Moves activation to the next activatable window.
   void CycleActivationForward();
 
+  void AddObserver(FocusControllerObserver* observer);
+  void RemoveObserver(FocusControllerObserver* observer);
+
  private:
-  // Describes the source of the change.
-  enum ChangeSource {
-    CHANGE_SOURCE_EXPLICIT,
-    CHANGE_SOURCE_DRAWN_STATE_CHANGED,
-  };
-
   // Returns whether |window| can be focused or activated.
   bool CanBeFocused(ServerWindow* window) const;
   bool CanBeActivated(ServerWindow* window) const;
 
   // Implementation of SetFocusedWindow().
-  void SetFocusedWindowImpl(ServerWindow* window, ChangeSource change_source);
+  void SetFocusedWindowImpl(FocusControllerChangeSource change_source,
+                            ServerWindow* window);
 
   // ServerWindowDrawnTrackerObserver:
   void OnDrawnStateChanged(ServerWindow* ancestor,
                            ServerWindow* window,
                            bool is_drawn) override;
 
-  FocusControllerDelegate* delegate_;
+  base::ObserverList<FocusControllerObserver> observers_;
   scoped_ptr<ServerWindowDrawnTracker> drawn_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(FocusController);
 };
 
 }  // namespace ws
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_FOCUS_CONTROLLER_H_