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

chrome/browser/appcache/chrome_appcache_service.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/appcache/chrome_appcache_service.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "chrome/browser/browser_list.h"
 #include "chrome/browser/cookie_prompt_modal_dialog_delegate.h"
@@ skipping 64 matching lines @@
 // static
 void ChromeAppCacheService::ClearLocalState(const FilePath& profile_path) {
   file_util::Delete(profile_path.Append(chrome::kAppCacheDirname), true);
 }
 
 bool ChromeAppCacheService::CanLoadAppCache(const GURL& manifest_url) {
   DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO));
   ContentSetting setting = host_contents_settings_map_->GetContentSetting(
       manifest_url, CONTENT_SETTINGS_TYPE_COOKIES);
   DCHECK(setting != CONTENT_SETTING_DEFAULT);
-  return setting == CONTENT_SETTING_ALLOW ||
-         setting == CONTENT_SETTING_ASK;  // we don't prompt for read access
+  // We don't prompt for read access.
+  return setting != CONTENT_SETTING_BLOCK;
 }
 
 int ChromeAppCacheService::CanCreateAppCache(
     const GURL& manifest_url, net::CompletionCallback* callback) {
   DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO));
   ContentSetting setting = host_contents_settings_map_->GetContentSetting(
       manifest_url, CONTENT_SETTINGS_TYPE_COOKIES);
   DCHECK(setting != CONTENT_SETTING_DEFAULT);
   if (setting == CONTENT_SETTING_ASK) {
     ChromeThread::PostTask(
@@ skipping 72 matching lines @@
     const tracked_objects::Location& from_here,
     Task* task) {
   return ChromeThread::PostTask(ToChromeThreadID(id), from_here, task);
 }
 
 bool AppCacheThread::CurrentlyOn(int id) {
   return ChromeThread::CurrentlyOn(ToChromeThreadID(id));
 }
 
 }  // namespace appcache