Give the main frame a RenderWidget.

content/public/test/mock_render_thread.cc

Index: content/public/test/mock_render_thread.cc
diff --git a/content/public/test/mock_render_thread.cc b/content/public/test/mock_render_thread.cc
index dee8514b68c6108e252a3bf5b467c706dac67f61..9e14339f355b1b34393ddbb62b50b5f169a6db42 100644
--- a/content/public/test/mock_render_thread.cc
+++ b/content/public/test/mock_render_thread.cc
@@ -215,14 +215,12 @@ void MockRenderThread::OnCreateWidget(int opener_id,
 // The View expects to be returned a valid route_id different from its own.
 void MockRenderThread::OnCreateWindow(
     const ViewHostMsg_CreateWindow_Params& params,
-    int* route_id,
-    int* main_frame_route_id,
-    int* surface_id,
-    int64* cloned_session_storage_namespace_id) {
-  *route_id = new_window_routing_id_;
-  *main_frame_route_id = new_window_main_frame_routing_id_;
-  *surface_id = surface_id_;
-  *cloned_session_storage_namespace_id = 0;
+    ViewHostMsg_CreateWindow_Reply* reply) {
+  reply->route_id = new_window_routing_id_;
+  reply->main_frame_route_id = new_window_main_frame_routing_id_;
+  // TODO(dcheng): Set main_frame_widget_route_id too??

[ncarter (slow), 2015/08/24 20:55:35]

You ought to at least set it to something, I think.
|new_window_main_frame_routing_id_| is always zero, fwiw.

[dcheng, 2015/09/03 16:33:09]

Done.

+  reply->surface_id = surface_id_;
+  reply->cloned_session_storage_namespace_id = 0;
 }
 
 // The Frame expects to be returned a valid route_id different from its own.