RenderWidget: make routing_id be a parameter of the ctor

content/renderer/render_widget_fullscreen.h

 // 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.
 
 #ifndef CONTENT_RENDERER_RENDER_WIDGET_FULLSCREEN_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_FULLSCREEN_H_
 
 #include "content/renderer/render_widget.h"
 
 #include <stdint.h>
 
 #include "third_party/WebKit/public/web/WebWidget.h"
 
 namespace content {
 class CompositorDependencies;
 
 // TODO(boliu): Override non-supported methods with no-op? eg setWindowRect().
 class RenderWidgetFullscreen : public RenderWidget {
  public:
   void show(blink::WebNavigationPolicy) override;
 
  protected:
-  RenderWidgetFullscreen(CompositorDependencies* compositor_deps,
+  static int32_t CreateFullscreenWidgetRoutingId(int32_t opener_id);
+
+  RenderWidgetFullscreen(int32_t widget_routing_id,
+                         CompositorDependencies* compositor_deps,
                          const ScreenInfo& screen_info);
   ~RenderWidgetFullscreen() override;
 
   virtual blink::WebWidget* CreateWebWidget();
 
   bool Init(int32_t opener_id);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_FULLSCREEN_H_