Moves WindowSelectorController onto WmShell

ash/wm/maximize_mode/maximize_mode_window_manager.cc

 // Copyright 2014 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/wm/maximize_mode/maximize_mode_window_manager.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/ash_switches.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_window_ids.h"
@@ skipping 18 matching lines @@
 
 namespace {
 
 // The height of the area in which a touch operation leads to exiting the
 // full screen mode.
 const int kLeaveFullScreenAreaHeightInPixel = 2;
 
 // Exits overview mode if it is currently active.
 void CancelOverview() {
   WindowSelectorController* controller =
-      Shell::GetInstance()->window_selector_controller();
-  if (controller && controller->IsSelecting())
+      WmShell::Get()->window_selector_controller();
+  if (controller->IsSelecting())
     controller->OnSelectionEnded();
 }
 
 }  // namespace
 
 MaximizeModeWindowManager::~MaximizeModeWindowManager() {
   // Overview mode needs to be ended before exiting maximize mode to prevent
   // transforming windows which are currently in
   // overview: http://crbug.com/366605
   CancelOverview();
@@ skipping 292 matching lines @@
     RootWindowController* controller = *iter;
     aura::Window* container = Shell::GetContainer(
         controller->GetRootWindow(), kShellWindowId_DefaultContainer);
     controller->workspace_controller()->SetMaximizeBackdropDelegate(
         std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate>(
             enable ? new WorkspaceBackdropDelegate(container) : NULL));
   }
 }
 
 }  // namespace ash