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

ash/host/ash_remote_window_tree_host_win.h

Index: ash/host/ash_remote_window_tree_host_win.h
diff --git a/ash/host/ash_remote_window_tree_host_win.h b/ash/host/ash_remote_window_tree_host_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..493a7b9bae06aef2f98dcc9d5c8a401938e199ce
--- /dev/null
+++ b/ash/host/ash_remote_window_tree_host_win.h
@@ -0,0 +1,53 @@
+// Copyright 2014 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 ASH_HOST_REMOTE_WINDOW_TREE_HOST_WIN_H_
+#define ASH_HOST_REMOTE_WINDOW_TREE_HOST_WIN_H_
+
+#include "ash/ash_export.h"
+#include "ash/host/ash_window_tree_host.h"
+#include "ash/host/transformer_helper.h"
+#include "ui/aura/remote_window_tree_host_win.h"
+
+namespace ash {
+
+class ASH_EXPORT AshRemoteWindowTreeHostWin
+    : public AshWindowTreeHost,
+      public aura::RemoteWindowTreeHostWin {
+ public:
+  // Creates an instance of AshRemoteWindowTreeHostWin
+  // and sets it to RemoteWindowTreeHostWin::SetInstance.
+  static void Init();
+
+  // Returns the instance created in Init() method above.
+  // This also performs an extra check if the instance is same
+  // one that aura::RemoteWindowTreeHostWin::Instance() returns.
+  static AshRemoteWindowTreeHostWin* GetInstance();
+
+ private:
+  AshRemoteWindowTreeHostWin();
+  virtual ~AshRemoteWindowTreeHostWin();
+
+  // AshWindowTreeHost:
+  virtual void ToggleFullScreen() OVERRIDE;
+  virtual bool ConfineCursorToRootWindow() OVERRIDE;
+  virtual void UnConfineCursor() OVERRIDE;
+  virtual void SetRootWindowTransformer(
+      scoped_ptr<RootWindowTransformer> transformer) OVERRIDE;
+  virtual aura::WindowTreeHost* AsWindowTreeHost() OVERRIDE;
+
+  // WindowTreeHostWin:
+  virtual gfx::Transform GetRootTransform() const OVERRIDE;
+  virtual void SetRootTransform(const gfx::Transform& transform) OVERRIDE;
+  virtual gfx::Transform GetInverseRootTransform() const OVERRIDE;
+  virtual void UpdateRootWindowSize(const gfx::Size& host_size) OVERRIDE;
+
+  TransformerHelper transformer_helper_;
+
+  DISALLOW_COPY_AND_ASSIGN(AshRemoteWindowTreeHostWin);
+};
+
+}  // namespace ash
+
+#endif  // ASH_HOST_REMOTE_WINDOW_TREE_HOST_WIN_H_