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

ui/aura/root_window_transformer.h

-// Copyright (c) 2013 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_ROOT_WINDOW_TRANSFORMER_H_
-#define UI_AURA_ROOT_WINDOW_TRANSFORMER_H_
-
-#include "ui/aura/aura_export.h"
-
-namespace gfx {
-class Insets;
-class Rect;
-class Size;
-class Transform;
-}
-
-namespace aura {
-
-// RootWindowTransformer controls how RootWindow should be placed and
-// transformed inside the host window.
-class AURA_EXPORT RootWindowTransformer {
- public:
-  virtual ~RootWindowTransformer() {}
-
-  // Returns the transform the root window in DIP.
-  virtual gfx::Transform GetTransform() const = 0;
-
-  // Returns the inverse of the transform above. This method is to
-  // provie an accurate inverse of the transform because the result of
-  // |gfx::Transform::GetInverse| may contains computational error.
-  virtual gfx::Transform GetInverseTransform() const = 0;
-
-  // Returns the root window's bounds for given host window size in DIP.
-  // This is necessary to handle the case where the root window's size
-  // is bigger than the host window. (Screen magnifier for example).
-  virtual gfx::Rect GetRootWindowBounds(const gfx::Size& host_size) const = 0;
-
-  // Returns the insets that specifies the effective area of
-  // the host window.
-  virtual gfx::Insets GetHostInsets() const = 0;
-};
-
-}  // namespace aura
-
-#endif  // UI_AURA_ROOT_WINDOW_TRANSFORMER_H_