Introdcue AshWindowTreeHost and move ash/chrome specific code in WTH to ash.

ash/magnifier/magnification_controller.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 "ash/magnifier/magnification_controller.h"
 
 #include "ash/accelerators/accelerator_controller.h"
 #include "ash/accessibility_delegate.h"
 #include "ash/ash_switches.h"
+#include "ash/host/ash_window_tree_host.h"
 #include "ash/display/root_window_transformers.h"
+#include "ash/host/root_window_transformer.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "base/command_line.h"
 #include "base/synchronization/waitable_event.h"
 #include "ui/aura/client/cursor_client.h"
-#include "ui/aura/root_window_transformer.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_property.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/compositor/dip_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animation_observer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/events/event.h"
 #include "ui/events/event_handler.h"
 #include "ui/gfx/point3_f.h"
@@ skipping 236 matching lines @@
       root_window_->layer()->GetAnimator());
   settings.AddObserver(this);
   settings.SetPreemptionStrategy(
       ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
   settings.SetTweenType(gfx::Tween::EASE_OUT);
   settings.SetTransitionDuration(
       base::TimeDelta::FromMilliseconds(animate ? 100 : 0));
 
   gfx::Display display =
       Shell::GetScreen()->GetDisplayNearestWindow(root_window_);
-  scoped_ptr<aura::RootWindowTransformer> transformer(
+  scoped_ptr<RootWindowTransformer> transformer(
       internal::CreateRootWindowTransformerForDisplay(root_window_, display));
-  root_window_->GetHost()->SetRootWindowTransformer(transformer.Pass());
+  AshWindowTreeHost::Get(root_window_)->SetRootWindowTransformer(transformer.Pass());
 
   if (animate)
     is_on_animation_ = true;
 
   return true;
 }
 
 void MagnificationControllerImpl::StartOrStopScrollIfNecessary() {
   // This value controls the scrolling speed.
   const int kMoveOffset = 40;
@@ skipping 310 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // MagnificationController:
 
 // static
 MagnificationController* MagnificationController::CreateInstance() {
   return new MagnificationControllerImpl();
 }
 
 }  // namespace ash