Refators display related functionality into own class

components/mus/ws/window_tree.h

 // 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.
 
 #ifndef COMPONENTS_MUS_WS_WINDOW_TREE_H_
 #define COMPONENTS_MUS_WS_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 16 matching lines @@
 namespace gfx {
 class Insets;
 class Rect;
 }
 
 namespace mus {
 namespace ws {
 
 class AccessPolicy;
 class ConnectionManager;
+class DisplayManager;
 class Display;
 class ServerWindow;
 class TargetedEvent;
 class WindowTreeTest;
 
 namespace test {
 class WindowTreeTestApi;
 }
 
 // WindowTree represents a view onto portions of the window tree. The parts of
@@ skipping 158 matching lines @@
   };
 
   enum class RemoveRootReason {
     // The window is being removed.
     DELETED,
 
     // Another connection is being embedded in the window.
     EMBED,
   };
 
+  DisplayManager* display_manager();
+  const DisplayManager* display_manager() const;
+
   // Used when this tree is the window manager.
   Display* GetDisplayForWindowManager();
 
   bool ShouldRouteToWindowManager(const ServerWindow* window) const;
 
   ClientWindowId ClientWindowIdForWindow(const ServerWindow* window) const;
 
   // Returns true if |id| is a valid WindowId for a new window.
   bool IsValidIdForNewWindow(const ClientWindowId& id) const;
 
@@ skipping 189 matching lines @@
 
   scoped_ptr<WaitingForTopLevelWindowInfo> waiting_for_top_level_window_info_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTree);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_WINDOW_TREE_H_