Fix showing the sibling menu on mouse move

ui/views/mus/mus_client.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 "ui/views/mus/mus_client.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread.h"
 #include "services/service_manager/public/cpp/connection.h"
@@ skipping 282 matching lines @@
 
 aura::Window* MusClient::GetWindowAtScreenPoint(const gfx::Point& point) {
   for (aura::Window* root : window_tree_client_->GetRoots()) {
     aura::WindowTreeHost* window_tree_host = root->GetHost();
     if (!window_tree_host)
       continue;
     // TODO: this likely gets z-order wrong. http://crbug.com/663606.
     gfx::Point relative_point(point);
     window_tree_host->ConvertScreenInPixelsToDIP(&relative_point);
     if (gfx::Rect(root->bounds().size()).Contains(relative_point))
-      return root->GetTopWindowContainingPoint(relative_point);
+      return root->GetEventHandlerForPoint(relative_point);
   }
   return nullptr;
 }
 
 }  // namespace views