Give the main frame a RenderWidget.

content/browser/renderer_host/render_view_host_impl.h

Index: content/browser/renderer_host/render_view_host_impl.h
diff --git a/content/browser/renderer_host/render_view_host_impl.h b/content/browser/renderer_host/render_view_host_impl.h
index 5889857b36b40ff33bd62790fb931cfecb8eaa37..83211f1bb86d9a38ae76493b0df96746ea4f40b2 100644
--- a/content/browser/renderer_host/render_view_host_impl.h
+++ b/content/browser/renderer_host/render_view_host_impl.h
@@ -291,11 +291,11 @@ class CONTENT_EXPORT RenderViewHostImpl : public RenderViewHost,
   gfx::Rect GetRootWindowResizerRect() const override;
 
   // Creates a new RenderView with the given route id.
-  void CreateNewWindow(
-      int route_id,
-      int main_frame_route_id,
-      const ViewHostMsg_CreateWindow_Params& params,
-      SessionStorageNamespace* session_storage_namespace);
+  void CreateNewWindow(int32_t route_id,
+                       int32_t main_frame_route_id,
+                       int32_t main_frame_widget_route_id,
+                       const ViewHostMsg_CreateWindow_Params& params,
+                       SessionStorageNamespace* session_storage_namespace);
 
   // Creates a new RenderWidget with the given route id.  |popup_type| indicates
   // if this widget is a popup and what kind of popup it is (select, autofill).