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

ash/host/ash_window_tree_host_ozone.cc

Index: ash/host/ash_window_tree_host_ozone.cc
diff --git a/ash/host/ash_window_tree_host_ozone.cc b/ash/host/ash_window_tree_host_ozone.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cfe8b25d336d93499e67c4bfb9bf9c27e970a091
--- /dev/null
+++ b/ash/host/ash_window_tree_host_ozone.cc
@@ -0,0 +1,40 @@
+// 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.
+
+#include "ash/host/ash_window_tree_host.h"
+
+#include "ash/host/root_window_transformer.h"
+#include "base/command_line.h"
+#include "ui/aura/window_tree_host_ozone.h"
+#include "ui/gfx/geometry/insets.h"
+
+namespace ash {
+namespace {
+
+class AshWindowTreeHostOzone : public AshWindowTreeHost,
+                               public aura::WindowTreeHostOzone {
+ public:
+  explicit AshWindowTreeHostOzone(const gfx::Rect& initial_bounds)
+      : aura::WindowTreeHostOzone(initial_bounds) {}
+  virtual ~AshWindowTreeHostOzone() {}
+
+ private:
+  // AshWindowTreeHost:
+  virtual void ToggleFullScreen() OVERRIDE { NOTIMPLEMENTED(); }
+  virtual bool ConfineCursorToRootWindow() OVERRIDE { return false; }
+  virtual void UnConfineCursor() OVERRIDE { NOTIMPLEMENTED(); }
+  virtual void SetRootWindowTransformer(
+      scoped_ptr<RootWindowTransformer> transformer) OVERRIDE {}
+  virtual aura::WindowTreeHost* AsWindowTreeHost() OVERRIDE { return this; }
+
+  DISALLOW_COPY_AND_ASSIGN(AshWindowTreeHostOzone);
+};
+
+}  // namespace
+
+AshWindowTreeHost* AshWindowTreeHost::Create(const gfx::Rect& initial_bounds) {
+  return new AshWindowTreeHostOzone(initial_bounds);
+}
+
+}  // namespace ash