Moves couple of WmShell methods to standalone functions

ash/common/wm/maximize_mode/maximize_mode_event_handler.cc

 // Copyright 2016 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/common/wm/maximize_mode/maximize_mode_event_handler.h"
 
 #include "ash/common/session/session_controller.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/common/wm/wm_event.h"
-#include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "ash/shell.h"
+#include "ash/wm/window_util.h"
 #include "ui/events/event.h"
 
 namespace ash {
 namespace wm {
 namespace {
 
 // The height of the area in which a touch operation leads to exiting the
 // full screen mode.
 const int kLeaveFullScreenAreaHeightInPixel = 2;
 
 }  // namespace
 
 MaximizeModeEventHandler::MaximizeModeEventHandler() {}
 
 MaximizeModeEventHandler::~MaximizeModeEventHandler() {}
 
 bool MaximizeModeEventHandler::ToggleFullscreen(const ui::TouchEvent& event) {
   if (event.type() != ui::ET_TOUCH_PRESSED)
     return false;
 
   const SessionController* controller = Shell::Get()->session_controller();
 
   if (controller->IsScreenLocked() ||
       controller->GetSessionState() != session_manager::SessionState::ACTIVE) {
     return false;
   }
 
   // Find the active window (from the primary screen) to un-fullscreen.
-  WmWindow* window = WmShell::Get()->GetActiveWindow();
+  WmWindow* window = WmWindow::Get(GetActiveWindow());
   if (!window)
     return false;
 
   WindowState* window_state = window->GetWindowState();
   if (!window_state->IsFullscreen() || window_state->in_immersive_fullscreen())
     return false;
 
   // Test that the touch happened in the top or bottom lines.
   int y = event.y();
   if (y >= kLeaveFullScreenAreaHeightInPixel &&
@@ skipping 10 matching lines @@
     return false;
   }
 
   WMEvent toggle_fullscreen(WM_EVENT_TOGGLE_FULLSCREEN);
   window->GetWindowState()->OnWMEvent(&toggle_fullscreen);
   return true;
 }
 
 }  // namespace wm
 }  // namespace ash