Give the main frame a RenderWidget.

content/browser/renderer_host/render_widget_helper.cc

 // 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.
 
 #include "content/browser/renderer_host/render_widget_helper.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/posix/eintr_wrapper.h"
@@ skipping 86 matching lines @@
 
 void RenderWidgetHelper::OnResumeDeferredNavigation(
     const GlobalRequestID& request_id) {
   resource_dispatcher_host_->ResumeDeferredNavigation(request_id);
 }
 
 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
     // open the window in a new BrowsingInstance, and thus a new process. That
     // means the current renderer process will not be able to route messages to
     // it. Because of this, we will immediately show and navigate the window
     // 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
     // be needed if a response ends up creating a plugin.
     resource_dispatcher_host_->BlockRequestsForRoute(
         render_process_id_, *route_id);
     resource_dispatcher_host_->BlockRequestsForRoute(
         render_process_id_, *main_frame_route_id);

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

Is this relevant for the third route as well?

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

Done.

   }
 
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&RenderWidgetHelper::OnCreateWindowOnUI,
                  this, params, *route_id, *main_frame_route_id,

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

If the main_frame_widget_route_id isn't passed to the UI thread or otherwise
recorded by the browser process, then is it good for anything? Or is hooking it
up the next phase of this work?

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

This was part of the incomplete browser-side plumbing. I've plumbed it through
now.

                  make_scoped_refptr(session_storage_namespace)));
 }
 
 void RenderWidgetHelper::OnCreateWindowOnUI(
     const ViewHostMsg_CreateWindow_Params& params,
     int route_id,
     int main_frame_route_id,
     SessionStorageNamespace* session_storage_namespace) {
   RenderViewHostImpl* host =
       RenderViewHostImpl::FromID(render_process_id_, params.opener_id);
@@ skipping 44 matching lines @@
 
 void RenderWidgetHelper::OnCreateFullscreenWidgetOnUI(int opener_id,
                                                       int route_id) {
   RenderViewHostImpl* host = RenderViewHostImpl::FromID(
       render_process_id_, opener_id);
   if (host)
     host->CreateNewFullscreenWidget(route_id);
 }
 
 }  // namespace content