Add a "session only" policy to the content settings.

chrome/browser/in_process_webkit/dom_storage_area.cc

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/in_process_webkit/dom_storage_area.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/task.h"
 #include "chrome/browser/chrome_thread.h"
@@ skipping 95 matching lines @@
                                         host_content_settings_map_);
     ChromeThread::PostTask(
         ChromeThread::UI, FROM_HERE,
         NewRunnableFunction(&DOMStoragePermissionRequest::PromptUser,
                             &request));
     // Tell the renderer that it needs to run a nested message loop.
     sender->Send(new ViewMsg_SignalCookiePromptEvent());
     content_setting = request.WaitOnResponse();
   }
 
-  if (content_setting == CONTENT_SETTING_ALLOW)
-    return true;
-  DCHECK(content_setting == CONTENT_SETTING_BLOCK);
-  return false;
+  return (content_setting != CONTENT_SETTING_BLOCK);
 }