When Chrome hands off a URL to be opened by the external host by the ViewHost...

chrome/test/automation/tab_proxy.cc

Index: chrome/test/automation/tab_proxy.cc
===================================================================
--- chrome/test/automation/tab_proxy.cc	(revision 29317)
+++ chrome/test/automation/tab_proxy.cc	(working copy)
@@ -108,12 +108,13 @@
 }
 
 AutomationMsg_NavigationResponseValues TabProxy::NavigateInExternalTab(
-    const GURL& url) {
+    const GURL& url, const GURL& referrer) {
   if (!is_valid())
     return AUTOMATION_MSG_NAVIGATION_ERROR;
 
   AutomationMsg_NavigationResponseValues rv = AUTOMATION_MSG_NAVIGATION_ERROR;
-  sender_->Send(new AutomationMsg_NavigateInExternalTab(0, handle_, url, &rv));
+  sender_->Send(new AutomationMsg_NavigateInExternalTab(0, handle_, url,
+                                                        referrer, &rv));
   return rv;
 }