Converts DockedWindowLayoutManager to use WmRootWindowControllerObserver

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,
     # These files lists are shared with the GN build.
     'ash_sources': [
       'accelerators/accelerator_commands.cc',
@@ skipping 532 matching lines @@
       'wm/common/window_positioning_utils.cc',
       'wm/common/window_positioning_utils.h',
       'wm/common/window_state_util.cc',
       'wm/common/window_state_util.h',
       'wm/common/wm_activation_observer.h',
       'wm/common/wm_event.cc',
       'wm/common/wm_event.h',
       'wm/common/wm_globals.h',
       'wm/common/wm_layout_manager.h',
       'wm/common/wm_root_window_controller.h',
+      'wm/common/wm_root_window_controller_observer.h',
       'wm/common/wm_screen_util.cc',
       'wm/common/wm_screen_util.h',
       'wm/common/wm_snap_to_pixel_layout_manager.cc',
       'wm/common/wm_snap_to_pixel_layout_manager.h',
       'wm/common/wm_types.cc',
       'wm/common/wm_types.h',
       'wm/common/wm_window.h',
       'wm/common/wm_window_observer.h',
       'wm/common/wm_window_property.h',
       'wm/common/workspace/workspace_layout_manager_delegate.h',
@@ skipping 830 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }