ProtectorService supports multiple change instances.

chrome/browser/automation/testing_automation_provider.cc

 // Copyright (c) 2012 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/automation/testing_automation_provider.h"
 
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 3444 matching lines @@
   AutomationJSONReply reply(this, reply_message);
   if (!protector::IsEnabled()) {
     reply.SendError("Protector is disabled");
     return;
   }
   std::string action;
   if (!args->GetString("action", &action)) {
     reply.SendError("Missing 'action' value");
     return;
   }
+  protector::BaseSettingChange* change =
+      protector_service->GetLastChange();
   if (action == "apply_change")
-    protector_service->ApplyChange(browser);
+    protector_service->ApplyChange(change, browser);
   else if (action == "discard_change")
-    protector_service->DiscardChange(browser);
+    protector_service->DiscardChange(change, browser);
   else
     return reply.SendError("Invalid 'action' value");
   reply.SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "GetLocalStatePrefsInfo" }
 // Refer chrome/test/pyautolib/prefs_info.py for sample json output.
 void TestingAutomationProvider::GetLocalStatePrefsInfo(
     DictionaryValue* args,
     IPC::Message* reply_message) {
@@ skipping 3494 matching lines @@
 
   Send(reply_message_);
   redirect_query_ = 0;
   reply_message_ = NULL;
 }
 
 void TestingAutomationProvider::OnRemoveProvider() {
   if (g_browser_process)
     g_browser_process->GetAutomationProviderList()->RemoveProvider(this);
 }