Adding GetEventSource() method to the WindowTreeHost class.

mojo/examples/aura_demo/window_tree_host_mojo.cc

 // Copyright (c) 2013 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 "mojo/examples/aura_demo/window_tree_host_mojo.h"
 
 #include "mojo/examples/aura_demo/demo_context_factory.h"
 #include "mojo/public/c/gles2/gles2.h"
 #include "mojo/public/cpp/bindings/allocation_scope.h"
 #include "mojo/services/native_viewport/geometry_conversions.h"
@@ skipping 38 matching lines @@
   CHECK(context_factory_) << "No GL bindings.";
 
   native_viewport_->CreateGLES2Context(gles2_client_handle.Pass());
 }
 
 WindowTreeHostMojo::~WindowTreeHostMojo() {}
 
 ////////////////////////////////////////////////////////////////////////////////
 // WindowTreeHostMojo, aura::WindowTreeHost implementation:
 
+ui::EventSource* WindowTreeHostMojo::GetEventSource() {
+  return this;
+}
+
 gfx::AcceleratedWidget WindowTreeHostMojo::GetAcceleratedWidget() {
   NOTIMPLEMENTED() << "GetAcceleratedWidget";
   return gfx::kNullAcceleratedWidget;
 }
 
 void WindowTreeHostMojo::Show() {
   window()->Show();
   native_viewport_->Show();
 }
 
@@ skipping 99 matching lines @@
       SendEventToProcessor(&ev);
       break;
     }
     // TODO(beng): touch, etc.
   }
   callback.Run();
 };
 
 }  // namespace examples
 }  // namespace mojo