Enable (optional) blocking of webrequests in case a PAC script cannot be fetched or is invalid.

chrome/browser/net/pref_proxy_config_service.cc

 // Copyright (c) 2011 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/pref_proxy_config_service.h"
 
 #include "base/values.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/pref_set_observer.h"
 #include "chrome/browser/prefs/proxy_config_dictionary.h"
@@ skipping 119 matching lines @@
         LOG(ERROR) << "Proxy settings request PAC script but do not specify "
                    << "its URL. Falling back to direct connection.";
         return true;
       }
       GURL proxy_pac_url(proxy_pac);
       if (!proxy_pac_url.is_valid()) {
         LOG(ERROR) << "Invalid proxy PAC url: " << proxy_pac;
         return true;
       }
       config->set_pac_url(proxy_pac_url);
+      bool pac_mandatory = false;
+      proxy_dict.GetPacMandatory(&pac_mandatory);
+      config->set_pac_mandatory(pac_mandatory);
       return true;
     }
     case ProxyPrefs::MODE_FIXED_SERVERS: {
       std::string proxy_server;
       if (!proxy_dict.GetProxyServer(&proxy_server)) {
         LOG(ERROR) << "Proxy settings request fixed proxy servers but do not "
                    << "specify their URLs. Falling back to direct connection.";
         return true;
       }
       config->proxy_rules().ParseFromString(proxy_server);
@@ skipping 111 matching lines @@
     pref_config_tracker_->AddObserver(this);
     registered_observers_ = true;
   }
 }
 
 // static
 void PrefProxyConfigService::RegisterPrefs(PrefService* pref_service) {
   DictionaryValue* default_settings = ProxyConfigDictionary::CreateSystem();
   pref_service->RegisterDictionaryPref(prefs::kProxy, default_settings);
 }