app_list: Fix shadow bleeds over launcher button and steals mouse events

ui/aura/demo/demo_main.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 "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/i18n/icu_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "third_party/skia/include/core/SkXfermode.h"
@@ skipping 50 matching lines @@
   }
   virtual bool CanFocus() OVERRIDE { return true; }
   virtual void OnCaptureLost() OVERRIDE {}
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE {
     canvas->DrawColor(color_, SkXfermode::kSrc_Mode);
   }
   virtual void OnDeviceScaleFactorChanged(float device_scale_factor) OVERRIDE {}
   virtual void OnWindowDestroying() OVERRIDE {}
   virtual void OnWindowDestroyed() OVERRIDE {}
   virtual void OnWindowVisibilityChanged(bool visible) OVERRIDE {}
+  virtual bool HasHitTestMask() const OVERRIDE { return false; }
+  virtual void GetHitTestMask(gfx::Path* mask) const OVERRIDE {}
 
  private:
   SkColor color_;
 
   DISALLOW_COPY_AND_ASSIGN(DemoWindowDelegate);
 };
 
 class DemoStackingClient : public aura::client::StackingClient {
  public:
   explicit DemoStackingClient(aura::RootWindow* root_window)
@@ skipping 62 matching lines @@
   window3.Show();
   window3.SetParent(&window2);
 
   root_window->ShowRootWindow();
   MessageLoopForUI::current()->Run();
 
   ui::CompositorTestSupport::Terminate();
 
   return 0;
 }