Refactor most recently used window tracking into a separate class.

ash/ash.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
     'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/chrome',
   },
   'includes': [
@@ skipping 400 matching lines @@
         'wm/gestures/two_finger_drag_handler.h',
         'wm/image_cursors.cc',
         'wm/image_cursors.h',
         'wm/lock_state_controller.cc',
         'wm/lock_state_controller.h',
         'wm/lock_state_controller_impl2.cc',
         'wm/lock_state_controller_impl2.h',
         'wm/lock_state_observer.h',
         'wm/maximize_bubble_controller.cc',
         'wm/maximize_bubble_controller.h',
+        'wm/mru_window_tracker.cc',
+        'wm/mru_window_tracker.h',
         'wm/overlay_event_filter.cc',
         'wm/overlay_event_filter.h',
         'wm/panels/panel_frame_view.cc',
         'wm/panels/panel_frame_view.h',
         'wm/panels/panel_layout_manager.cc',
         'wm/panels/panel_layout_manager.h',
         'wm/panels/panel_window_event_handler.cc',
         'wm/panels/panel_window_event_handler.h',
         'wm/panels/panel_window_resizer.cc',
         'wm/panels/panel_window_resizer.h',
@@ skipping 472 matching lines @@
             'shell/cocoa/app-Info.plist',
           ],
           'xcode_settings': {
             'INFOPLIST_FILE': 'shell/cocoa/app-Info.plist',
           },
         }],
       ],
     },
   ],
 }