Use a mocked compositor for unit tests

ui/aura/desktop.cc

 // 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.
 
 #include "ui/aura/desktop.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "ui/aura/desktop_delegate.h"
@@ skipping 15 matching lines @@
 // static
 ui::Compositor*(*Desktop::compositor_factory_)() = NULL;
 
 Desktop::Desktop()
     : delegate_(NULL),
       host_(aura::DesktopHost::Create(gfx::Rect(200, 200, 1280, 1024))),
       ALLOW_THIS_IN_INITIALIZER_LIST(schedule_paint_factory_(this)),
       active_window_(NULL),
       in_destructor_(false) {
   if (compositor_factory_) {
-    compositor_ = (*Desktop::compositor_factory())();
+    compositor_ = (*Desktop::compositor_factory())(this);
   } else {
     compositor_ = ui::Compositor::Create(this, host_->GetAcceleratedWidget(),
                                          host_->GetSize());
   }
   gfx::Screen::SetInstance(new internal::ScreenAura);
   host_->SetDesktop(this);
   DCHECK(compositor_.get());
   window_.reset(new internal::RootWindow);
 }
 
@@ skipping 120 matching lines @@
 // static
 Desktop* Desktop::GetInstance() {
   if (!instance_) {
     instance_ = new Desktop;
     instance_->Init();
   }
   return instance_;
 }
 
 }  // namespace aura