Give the main frame a RenderWidget.

content/browser/frame_host/render_frame_host_manager.cc

Index: content/browser/frame_host/render_frame_host_manager.cc
diff --git a/content/browser/frame_host/render_frame_host_manager.cc b/content/browser/frame_host/render_frame_host_manager.cc
index 1d36b037795c5cd216fadeb4f67851c11f9e1101..e1c9d71960520fc3c6639850bc6f3b438f702a50 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -253,17 +253,16 @@ RenderFrameHostManager::~RenderFrameHostManager() {
   SetRenderFrameHost(scoped_ptr<RenderFrameHostImpl>());
 }
 
-void RenderFrameHostManager::Init(BrowserContext* browser_context,
-                                  SiteInstance* site_instance,
+void RenderFrameHostManager::Init(SiteInstance* site_instance,
                                   int32 view_routing_id,
                                   int32 frame_routing_id,
                                   int32 widget_routing_id) {
-  // Create a RenderViewHost and RenderFrameHost, once we have an instance.  It
-  // is important to immediately give this SiteInstance to a RenderViewHost so
-  // that the SiteInstance is ref counted.
-  if (!site_instance)
-    site_instance = SiteInstance::Create(browser_context);
-
+  DCHECK(site_instance);
+  // TODO(avi): While RenderViewHostImpl is-a RenderWidgetHostImpl, this must
+  // hold true to avoid having two RenderWidgetHosts for the top-level frame.
+  // https://crbug.com/545684
+  DCHECK_IMPLIES(frame_tree_node_->IsMainFrame(),
+                 view_routing_id == widget_routing_id);
   int flags = delegate_->IsHidden() ? CREATE_RF_HIDDEN : 0;
   SetRenderFrameHost(CreateRenderFrameHost(site_instance, view_routing_id,
                                            frame_routing_id, widget_routing_id,
@@ -1802,6 +1801,7 @@ scoped_ptr<RenderFrameHostImpl> RenderFrameHostManager::CreateRenderFrame(
   } else {
     // Create a new RenderFrameHost if we don't find an existing one.
 
+    int32 view_routing_id = MSG_ROUTING_NONE;
     int32 widget_routing_id = MSG_ROUTING_NONE;
     // A RenderFrame in a different process from its parent RenderFrame
     // requires a RenderWidget for input/layout/painting.
@@ -1810,10 +1810,15 @@ scoped_ptr<RenderFrameHostImpl> RenderFrameHostManager::CreateRenderFrame(
             instance) {
       CHECK(SiteIsolationPolicy::AreCrossProcessFramesPossible());
       widget_routing_id = instance->GetProcess()->GetNextRoutingID();
+    } else if (!frame_tree_node_->parent()) {
+      // TODO(avi): This branch can be merged with the above branch once
+      // RenderViewHostImpl has-a RenderWidgetHostImpl. https://crbug.com/545684
+      view_routing_id = widget_routing_id =
+          instance->GetProcess()->GetNextRoutingID();
     }
 
     new_render_frame_host = CreateRenderFrameHost(
-        instance, MSG_ROUTING_NONE, MSG_ROUTING_NONE, widget_routing_id, flags);
+        instance, view_routing_id, MSG_ROUTING_NONE, widget_routing_id, flags);
     RenderViewHostImpl* render_view_host =
         new_render_frame_host->render_view_host();
     int proxy_routing_id = MSG_ROUTING_NONE;