Fixes aura unit tests. There were a couple of problems:

ui/aura/event_filter.h

 // Copyright (c) 2011 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 UI_AURA_EVENT_FILTER_H_
 #define UI_AURA_EVENT_FILTER_H_
 #pragma once
 
 #include "base/logging.h"
 #include "ui/gfx/point.h"
 
 namespace aura {
 
 class Window;
 class MouseEvent;
 
 // An object that filters events sent to an owner window, potentially performing
 // adjustments to the window's position, size and z-index.
 class EventFilter {
  public:
   explicit EventFilter(Window* owner);
   virtual ~EventFilter();
 
   // Try to handle |event| (before the owner's delegate gets a chance to).
   // Returns true if the event was handled by the WindowManager and should not
   // be forwarded to the owner's delegate.
+  // Default implementation for ET_MOUSE_PRESSED focuses the window.
   virtual bool OnMouseEvent(Window* target, MouseEvent* event);
 
  protected:
   Window* owner() { return owner_; }
 
  private:
   Window* owner_;
 
   DISALLOW_COPY_AND_ASSIGN(EventFilter);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_EVENT_FILTER_H_