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

chrome/browser/appcache/chrome_appcache_service.cc

Index: chrome/browser/appcache/chrome_appcache_service.cc
diff --git a/chrome/browser/appcache/chrome_appcache_service.cc b/chrome/browser/appcache/chrome_appcache_service.cc
index 1939a168b52ae09c761ca1947ea38d63684e4b48..c2e41a0c88e039b9da5364299dc840e5c6e16a67 100644
--- a/chrome/browser/appcache/chrome_appcache_service.cc
+++ b/chrome/browser/appcache/chrome_appcache_service.cc
@@ -82,8 +82,8 @@ bool ChromeAppCacheService::CanLoadAppCache(const GURL& manifest_url) {
   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(