Makes construction of (ash)RemoteWindowTreeHostWin explicit

ash/host/ash_remote_window_tree_host_win.h

 // 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 <windows.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();
+  explicit AshRemoteWindowTreeHostWin(HWND remote_hwnd);
 
  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 gfx::Insets GetHostInsets() const 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_