Moves MruWindowTracker to WmShell

ash/common/wm_shell.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_shell.h"
 
+#include "ash/common/wm/mru_window_tracker.h"
+
 namespace ash {
 
 // static
 WmShell* WmShell::instance_ = nullptr;
 
 // static
 void WmShell::Set(WmShell* instance) {
   instance_ = instance;
 }
 
 // static
 WmShell* WmShell::Get() {
   return instance_;
 }
 
+WmShell::WmShell() {}
+
+WmShell::~WmShell() {}
+
+void WmShell::CreateMruWindowTracker() {
+  mru_window_tracker_.reset(new MruWindowTracker);
+}
+
+void WmShell::DeleteMruWindowTracker() {
+  mru_window_tracker_.reset();
+}
+
 }  // namespace ash