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

chrome/browser/net/chrome_cookie_policy.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/net/chrome_cookie_policy.h"
 
 #include "base/string_util.h"
 #include "chrome/browser/browser_list.h"
 #include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/cookie_prompt_modal_dialog_delegate.h"
@@ skipping 126 matching lines @@
   return policy;
 }
 
 int ChromeCookiePolicy::CheckPolicy(const GURL& url) const {
   ContentSetting setting = host_content_settings_map_->GetContentSetting(
       url, CONTENT_SETTINGS_TYPE_COOKIES);
   if (setting == CONTENT_SETTING_BLOCK)
     return net::ERR_ACCESS_DENIED;
   if (setting == CONTENT_SETTING_ALLOW)
     return net::OK;
+  if (setting == CONTENT_SETTING_SESSION_ONLY)
+    return net::OK_FOR_SESSION_ONLY;
   return net::ERR_IO_PENDING;  // Need to prompt.
 }
 
 void ChromeCookiePolicy::PromptForSetCookie(const GURL& url,
                                             const std::string& cookie_line) {
   if (!ChromeThread::CurrentlyOn(ChromeThread::UI)) {
     ChromeThread::PostTask(
         ChromeThread::UI, FROM_HERE,
         NewRunnableMethod(this, &ChromeCookiePolicy::PromptForSetCookie, url,
                           cookie_line));
@@ skipping 55 matching lines @@
     callbacks.push_back(completions[i].callback());
   }
   completions.erase(completions.begin(), completions.begin() + i);
 
   if (completions.empty())
     host_completions_map_.erase(it);
 
   for (size_t j = 0; j < callbacks.size(); ++j)
     callbacks[j]->Run(policy);
 }