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

ui/aura/window.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/window.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "ui/aura/desktop.h"
@@ skipping 108 matching lines @@
 void Window::MoveChildToFront(Window* child) {
   DCHECK_EQ(child->parent(), this);
   const Windows::iterator i(std::find(children_.begin(), children_.end(),
                                       child));
   DCHECK(i != children_.end());
   children_.erase(i);
 
   // TODO(beng): this obviously has to handle different window types.
   children_.insert(children_.begin() + children_.size(), child);
   SchedulePaintInRect(gfx::Rect());
+
+  ui::Layer* parent_layer = child->layer()->parent();
+  parent_layer->Remove(child->layer());
+  parent_layer->Add(child->layer());
 }
 
 void Window::AddChild(Window* child) {
   DCHECK(std::find(children_.begin(), children_.end(), child) ==
       children_.end());
   child->parent_ = this;
   layer_->Add(child->layer_.get());
   children_.push_back(child);
 }
 
@@ skipping 58 matching lines @@
 
 void Window::SchedulePaint() {
   SchedulePaintInRect(gfx::Rect(0, 0, bounds_.width(), bounds_.height()));
 }
 
 void Window::OnPaintLayer(gfx::Canvas* canvas) {
   delegate_->OnPaint(canvas);
 }
 
 }  // namespace aura