Add rudimentary support in the ChromeFrame ActiveX to enable it work in a generic client site, i.e.

chrome_frame/chrome_frame_activex.h

 // Copyright (c) 2011 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_ACTIVEX_H_
 #define CHROME_FRAME_CHROME_FRAME_ACTIVEX_H_
 
 #include <atlbase.h>
 #include <atlcom.h>
 #include <atlctl.h>
@@ skipping 121 matching lines @@
 
   // This variant is used for the privatemessage handler only.
   void FireEvent(const EventHandlers& handlers, IDispatch* event,
                  BSTR target);
 
   // Installs a hook on the top-level window hosting the control.
   HRESULT InstallTopLevelHook(IOleClientSite* client_site);
 
   // A hook attached to the top-level window containing the ActiveX control.
   HHOOK chrome_wndproc_hook_;
+
+  // Set to true if the current instance is attaching to an existing Chrome
+  // tab. This occurs when a window.open request is performed by Chrome.
+  bool attaching_to_existing_cf_tab_;
 };
 
 #endif  // CHROME_FRAME_CHROME_FRAME_ACTIVEX_H_