RenderWidget: make routing_id be a parameter of the ctor

content/renderer/render_widget_fullscreen.h

Index: content/renderer/render_widget_fullscreen.h
diff --git a/content/renderer/render_widget_fullscreen.h b/content/renderer/render_widget_fullscreen.h
index a73f9db2620329abaaa0e42f6507a80a727792d4..5908d1cde36c49a77a3e698dbd1c742e2813af55 100644
--- a/content/renderer/render_widget_fullscreen.h
+++ b/content/renderer/render_widget_fullscreen.h
@@ -20,7 +20,10 @@ class RenderWidgetFullscreen : public RenderWidget {
   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;