Attempt 2 at landing this....

chrome_frame/chrome_frame_activex_base.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_ACTIVEX_BASE_H_
 #define CHROME_FRAME_CHROME_FRAME_ACTIVEX_BASE_H_
 
 #include <atlbase.h>
 #include <atlcom.h>
 #include <atlctl.h>
@@ skipping 24 matching lines @@
 #include "base/scoped_comptr_win.h"
 #include "base/scoped_variant_win.h"
 #include "base/string_util.h"
 #include "grit/chrome_frame_resources.h"
 #include "grit/chrome_frame_strings.h"
 #include "chrome_frame/chrome_frame_plugin.h"
 #include "chrome_frame/com_message_event.h"
 #include "chrome_frame/com_type_info_holder.h"
 #include "chrome_frame/urlmon_url_request.h"
 #include "grit/generated_resources.h"
+#include "net/base/cookie_monster.h"
 
 // Include without path to make GYP build see it.
 #include "chrome_tab.h"  // NOLINT
 
 // Connection point class to support firing IChromeFrameEvents (dispinterface).
 template<class T>
 class ATL_NO_VTABLE ProxyDIChromeFrameEvents
     : public IConnectionPointImpl<T, &DIID_DIChromeFrameEvents> {
  public:
   void FireMethodWithParams(ChromeFrameEventDispId dispid,
@@ skipping 461 matching lines @@
     if (request) {
       static_cast<UrlmonUrlRequest*>(request)->TransferToHost(doc_site_);
     }
     automation_client_->RemoveRequest(request_id, false);
   }
 
   virtual void OnSetCookieAsync(int tab_handle, const GURL& url,
                                 const std::string& cookie) {
     std::string name;
     std::string data;
+
     size_t name_end = cookie.find('=');
     if (std::string::npos != name_end) {
-      name = cookie.substr(0, name_end);
-      data = cookie.substr(name_end + 1);
+      net::CookieMonster::ParsedCookie parsed_cookie = cookie;
+      name = parsed_cookie.Name();
+      // Verify if the cookie is being deleted. The cookie format is as below
+      // value[; expires=date][; domain=domain][; path=path][; secure]
+      // If the first semicolon appears immediately after the name= string,
+      // it means that the cookie is being deleted.
+      if (!parsed_cookie.Value().empty())
+        data = cookie.substr(name_end + 1);
     } else {
       data = cookie;
     }
 
     BOOL ret = InternetSetCookieA(url.spec().c_str(), name.c_str(),
                                   data.c_str());
     DCHECK(ret) << "InternetSetcookie failed. Error: " << GetLastError();
   }
 
   virtual void OnAttachExternalTab(int tab_handle,
@@ skipping 592 matching lines @@
   EventHandlers onprivatemessage_;
   EventHandlers onextensionready_;
 
   // The UrlmonUrlRequest instance instantiated for downloading the base URL.
   scoped_refptr<CComObject<UrlmonUrlRequest> > base_url_request_;
 
   base::Thread worker_thread_;
 };
 
 #endif  // CHROME_FRAME_CHROME_FRAME_ACTIVEX_BASE_H_