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

chrome_frame/test/chrome_frame_automation_mock.h

 // Copyright (c) 2006-2009 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_TEST_CHROME_FRAME_AUTOMATION_MOCK_H_
 #define CHROME_FRAME_TEST_CHROME_FRAME_AUTOMATION_MOCK_H_
 
 #include <string>
 
 #include "base/file_path.h"
 #include "base/path_service.h"
@@ skipping 23 matching lines @@
     }
     if (IsWindow())
       DestroyWindow();
 
     test_server_.TearDown();
   }
 
   // Navigate external tab to the specified url through automation
   bool Navigate(const std::string& url) {
     url_ = GURL(url);
-    return automation_client_->InitiateNavigation(url, false);
+    return automation_client_->InitiateNavigation(url, std::string(), false);
   }
 
   // Navigate the external to a 'file://' url for unit test files
   bool NavigateRelativeFile(const std::wstring& file) {
     FilePath cf_source_path;
     PathService::Get(base::DIR_SOURCE_ROOT, &cf_source_path);
     std::wstring file_url(L"file://");
     file_url.append(cf_source_path.Append(
         FILE_PATH_LITERAL("chrome_frame")).Append(
             FILE_PATH_LITERAL("test")).Append(
@@ skipping 144 matching lines @@
   virtual void OnLoad(int tab_handle, const GURL& url) {
     Base::OnLoad(tab_handle, url);
   }
  private:
   bool request_start_result_;
 };
 
 
 #endif  // CHROME_FRAME_TEST_CHROME_FRAME_AUTOMATION_MOCK_H_