Makes display roots be destroyed by client

services/ui/ws/display.h

 // Copyright 2015 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 SERVICES_UI_WS_DISPLAY_H_
 #define SERVICES_UI_WS_DISPLAY_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 137 matching lines @@
   void UpdateNativeCursor(int32_t cursor_id);
 
   // mojom::WindowTreeHost:
   void SetSize(const gfx::Size& size) override;
   void SetTitle(const mojo::String& title) override;
 
  private:
   friend class test::DisplayTestApi;
 
   using WindowManagerDisplayRootMap =
-      std::map<UserId, std::unique_ptr<WindowManagerDisplayRoot>>;
+      std::map<UserId, WindowManagerDisplayRoot*>;
 
   // Inits the necessary state once the display is ready.
   void InitWindowManagerDisplayRootsIfNecessary();
 
   // Creates the set of WindowManagerDisplayRoots from the
   // WindowManagerWindowTreeFactorySet.
   void CreateWindowManagerDisplayRootsFromFactories();
 
   void CreateWindowManagerDisplayRootFromFactory(
       WindowManagerWindowTreeFactory* factory);
@@ skipping 47 matching lines @@
 
   WindowManagerDisplayRootMap window_manager_display_root_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Display);
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_DISPLAY_H_