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

chrome_frame/chrome_frame_delegate.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_FRAME_CHROME_FRAME_DELEGATE_H_
 #define CHROME_FRAME_CHROME_FRAME_DELEGATE_H_
 
 #include "chrome/test/automation/automation_messages.h"
 #include "ipc/ipc_message.h"
 
@@ skipping 51 matching lines @@
 
  protected:
   // Protected methods to be overriden.
   virtual void OnNavigationStateChanged(int tab_handle, int flags,
                                         const IPC::NavigationInfo& nav_info) {}
   virtual void OnUpdateTargetUrl(int tab_handle,
                                  const std::wstring& new_target_url) {}
   virtual void OnAcceleratorPressed(int tab_handle, const MSG& accel_message) {}
   virtual void OnTabbedOut(int tab_handle, bool reverse) {}
   virtual void OnOpenURL(int tab_handle, const GURL& url,
-                         int open_disposition) {}
+                         const GURL& referrer, int open_disposition) {}
   virtual void OnDidNavigate(int tab_handle,
                              const IPC::NavigationInfo& navigation_info) {}
   virtual void OnNavigationFailed(int tab_handle, int error_code,
                                   const GURL& gurl) {}
   virtual void OnLoad(int tab_handle, const GURL& url) {}
   virtual void OnMessageFromChromeFrame(int tab_handle,
                                         const std::string& message,
                                         const std::string& origin,
                                         const std::string& target) {}
   virtual void OnHandleContextMenu(int tab_handle, HANDLE menu_handle,
                                    int x_pos, int y_pos, int align_flags) {}
   virtual void OnRequestStart(int tab_handle, int request_id,
                               const IPC::AutomationURLRequest& request) {}
   virtual void OnRequestRead(int tab_handle, int request_id,
                              int bytes_to_read) {}
   virtual void OnRequestEnd(int tab_handle, int request_id,
                             const URLRequestStatus& status) {}
   virtual void OnSetCookieAsync(int tab_handle, const GURL& url,
                                 const std::string& cookie) {}
   virtual void OnAttachExternalTab(int tab_handle, intptr_t cookie,
                                    int disposition) {}
   virtual void OnGoToHistoryEntryOffset(int tab_handle, int offset) {}
 };
 
 #endif  // CHROME_FRAME_CHROME_FRAME_DELEGATE_H_