Change OnWindowInputEvent to use display_id to find the host and update event root_location in WS.

services/ui/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 SERVICES_UI_WS_WINDOW_TREE_H_
 #define SERVICES_UI_WS_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 100 matching lines @@
   }
   // Returns whether |window| is known to this tree. If |window| is known and
   // |client_window_id| is non-null |client_window_id| is set to the
   // ClientWindowId of the window.
   bool IsWindowKnown(const ServerWindow* window,
                      ClientWindowId* client_window_id) const;
 
   // Returns true if |window| is one of this trees roots.
   bool HasRoot(const ServerWindow* window) const;
 
+  // Find the correct root for |window| in this tree's roots.
+  const ServerWindow* FindRootFor(const ServerWindow* window) const;
+
   std::set<const ServerWindow*> roots() { return roots_; }
 
   void set_name(const std::string& name) { name_ = name; }
   const std::string& name() const { return name_; }
 
   bool janky() const { return janky_; }
 
   const Display* GetDisplay(const ServerWindow* window) const;
   Display* GetDisplay(const ServerWindow* window) {
     return const_cast<Display*>(
@@ skipping 451 matching lines @@
       waiting_for_top_level_window_info_;
   bool embedder_intercepts_events_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTree);
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_WINDOW_TREE_H_