Using WmDisplayObserver in ScreenPinningController.

ash/shell.cc

 // 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.
 
 #include "ash/shell.h"
 
 #include <algorithm>
 #include <string>
 #include <utility>
 
@@ skipping 960 matching lines @@
 
   toplevel_window_event_handler_.reset(
       new ToplevelWindowEventHandler(wm_shell_.get()));
 
   if (!is_mash) {
     system_gesture_filter_.reset(new SystemGestureEventFilter);
     AddPreTargetHandler(system_gesture_filter_.get());
   }
 
   sticky_keys_controller_.reset(new StickyKeysController);
-  if (!is_mash) {
-    screen_pinning_controller_.reset(
-        new ScreenPinningController(window_tree_host_manager_.get()));
-  }
+  if (!is_mash)
+    screen_pinning_controller_ = base::MakeUnique<ScreenPinningController>();
 
   lock_state_controller_ =
       base::MakeUnique<LockStateController>(shutdown_controller_.get());
   power_button_controller_.reset(
       new PowerButtonController(lock_state_controller_.get()));
   // Pass the initial display state to PowerButtonController.
   power_button_controller_->OnDisplayModeChanged(
       display_configurator_->cached_displays());
 
   AddShellObserver(lock_state_controller_.get());
@@ skipping 249 matching lines @@
 
   // Only trigger an update in mash because with classic ash chrome calls
   // UpdateAfterLoginStatusChange() directly.
   if (wm_shell_->IsRunningInMash()) {
     // TODO(jamescook): Should this call Shell::OnLoginStatusChanged() too?
     UpdateAfterLoginStatusChange(session_controller_->GetLoginStatus());
   }
 }
 
 }  // namespace ash