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

chrome/browser/cocoa/content_exceptions_window_controller.mm

 // 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.
 
 #import "chrome/browser/cocoa/content_exceptions_window_controller.h"
 
 #include "app/l10n_util_mac.h"
 #include "app/table_model_observer.h"
 #import "base/mac_util.h"
 #import "base/scoped_nsobject.h"
@@ skipping 110 matching lines @@
 
 const CGFloat kButtonBarHeight = 35.0;
 
 // The settings shown in the combobox if showAsk_ is false;
 const ContentSetting kNoAskSettings[] = { CONTENT_SETTING_ALLOW,
                                           CONTENT_SETTING_BLOCK };
 
 // The settings shown in the combobox if showAsk_ is true;
 const ContentSetting kAskSettings[] = { CONTENT_SETTING_ALLOW,
                                         CONTENT_SETTING_ASK,
+                                        CONTENT_SETTING_SESSION_ONLY,
                                         CONTENT_SETTING_BLOCK };
 
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // ContentExceptionsWindowController implementation
 
 static ContentExceptionsWindowController*
     g_exceptionWindows[CONTENT_SETTINGS_NUM_TYPES] = { nil };
 
@@ skipping 328 matching lines @@
 }
 
 - (NSString*)titleForIndex:(size_t)index {
   switch ([self settingForIndex:index]) {
     case CONTENT_SETTING_ALLOW:
       return l10n_util::GetNSStringWithFixup(IDS_EXCEPTIONS_ALLOW_BUTTON);
     case CONTENT_SETTING_BLOCK:
       return l10n_util::GetNSStringWithFixup(IDS_EXCEPTIONS_BLOCK_BUTTON);
     case CONTENT_SETTING_ASK:
       return l10n_util::GetNSStringWithFixup(IDS_EXCEPTIONS_ASK_BUTTON);
+    case CONTENT_SETTING_SESSION_ONLY:
+      return l10n_util::GetNSStringWithFixup(
+          IDS_EXCEPTIONS_SESSION_ONLY_BUTTON);
     default:
       NOTREACHED();
   }
   return @"";
 }
 
 - (ContentSetting)settingForIndex:(size_t)index {
   return showAsk_ ? kAskSettings[index] : kNoAskSettings[index];
 }
 
 - (size_t)indexForSetting:(ContentSetting)setting {
   for (size_t i = 0; i < [self menuItemCount]; ++i) {
     if ([self settingForIndex:i] == setting)
       return i;
   }
   NOTREACHED();
   return 0;
 }
 
 @end