Makes it so each windowtreeclient can use whatever ids it wants

components/mus/ws/window_tree_host_impl.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 COMPONENTS_MUS_WS_WINDOW_TREE_HOST_IMPL_H_
 #define COMPONENTS_MUS_WS_WINDOW_TREE_HOST_IMPL_H_
 
 #include <stdint.h>
 
 #include <queue>
@@ skipping 139 matching lines @@
   // The second case happens if EventDispatcher generates more than one event
   // at a time.
   struct QueuedEvent {
     QueuedEvent();
     ~QueuedEvent();
 
     mojom::EventPtr event;
     scoped_ptr<ProcessedEventTarget> processed_target;
   };
 
-  WindowId MapWindowIdFromClient(Id transport_window_id) const;
+  // Returns the ServerWindow with the specified transport id. Use this *only*
+  // if the call originates WindowTreeImpl associated with GetWindowTree().
+  ServerWindow* GetWindowFromWindowTreeHost(Id transport_window_id);
 
   void OnClientClosed();
 
   void OnEventAckTimeout();
 
   // Schedules an event to be processed later.
   void QueueEvent(mojom::EventPtr event,
                   scoped_ptr<ProcessedEventTarget> processed_event_target);
 
   // Processes the next valid event in |event_queue_|. If the event has already
@@ skipping 64 matching lines @@
 
   mojom::FrameDecorationValuesPtr frame_decoration_values_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeHostImpl);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_WINDOW_TREE_HOST_IMPL_H_