Adding GetEventSource() method to the WindowTreeHost class.

ui/aura/window_tree_host_x11.cc

 // Copyright (c) 2012 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/aura/window_tree_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
@@ skipping 324 matching lines @@
       }
 
       ui::MouseEvent mouseev(xev);
       TranslateAndDispatchLocatedEvent(&mouseev);
       break;
     }
   }
   return ui::POST_DISPATCH_STOP_PROPAGATION;
 }
 
+ui::EventSource* WindowTreeHostX11::GetEventSource() {
+  return this;
+}
+
 gfx::AcceleratedWidget WindowTreeHostX11::GetAcceleratedWidget() {
   return xwindow_;
 }
 
 void WindowTreeHostX11::Show() {
   if (!window_mapped_) {
     // Before we map the window, set size hints. Otherwise, some window managers
     // will ignore toplevel XMoveWindow commands.
     XSizeHints size_hints;
     size_hints.flags = PPosition | PWinGravity;
@@ skipping 267 matching lines @@
 }
 
 namespace test {
 
 void SetUseOverrideRedirectWindowByDefault(bool override_redirect) {
   default_override_redirect = override_redirect;
 }
 
 }  // namespace test
 }  // namespace aura