Give the main frame a RenderWidget.

content/browser/renderer_host/render_widget_helper.cc

Index: content/browser/renderer_host/render_widget_helper.cc
diff --git a/content/browser/renderer_host/render_widget_helper.cc b/content/browser/renderer_host/render_widget_helper.cc
index 4bd7af0a1212c127f8b18f55bf4399836930ab0d..298194a45164f41653ec830bb7314cae36128775 100644
--- a/content/browser/renderer_host/render_widget_helper.cc
+++ b/content/browser/renderer_host/render_widget_helper.cc
@@ -104,9 +104,10 @@ void RenderWidgetHelper::CreateNewWindow(
     const ViewHostMsg_CreateWindow_Params& params,
     bool no_javascript_access,
     base::ProcessHandle render_process,
-    int* route_id,
-    int* main_frame_route_id,
-    int* surface_id,
+    int32* route_id,
+    int32* main_frame_route_id,
+    int32* main_frame_widget_route_id,
+    int32* surface_id,
     SessionStorageNamespace* session_storage_namespace) {
   if (params.opener_suppressed || no_javascript_access) {
     // If the opener is supppressed or script access is disallowed, we should
@@ -116,10 +117,12 @@ void RenderWidgetHelper::CreateNewWindow(
     // in OnCreateWindowOnUI, using the params provided here.
     *route_id = MSG_ROUTING_NONE;
     *main_frame_route_id = MSG_ROUTING_NONE;
+    *main_frame_widget_route_id = MSG_ROUTING_NONE;
     *surface_id = 0;
   } else {
     *route_id = GetNextRoutingID();
     *main_frame_route_id = GetNextRoutingID();
+    *main_frame_widget_route_id = GetNextRoutingID();
     *surface_id = GpuSurfaceTracker::Get()->AddSurfaceForRenderer(
         render_process_id_, *route_id);
     // Block resource requests until the view is created, since the HWND might