Supervised users: Add a cmdline flag and about:flags entry to enable the host blacklist

chrome/browser/supervised_user/supervised_user_service.cc

 // Copyright 2014 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/supervised_user/supervised_user_service.h"
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/pref_service.h"
@@ skipping 697 matching lines @@
                    base::Unretained(this)));
     pref_change_registrar_.Add(prefs::kSupervisedUserManualURLs,
         base::Bind(&SupervisedUserService::UpdateManualURLs,
                    base::Unretained(this)));
 
     // Initialize the filter.
     OnDefaultFilteringBehaviorChanged();
     UpdateSiteLists();
     UpdateManualHosts();
     UpdateManualURLs();
-    if (delegate_) {
+    bool use_blacklist =
+        CommandLine::ForCurrentProcess()->HasSwitch(
+            switches::kEnableSupervisedUserBlacklist);
+    if (delegate_ && use_blacklist) {
       base::FilePath blacklist_path = delegate_->GetBlacklistPath();
       if (!blacklist_path.empty())
         LoadBlacklist(blacklist_path);
     }
 
 #if !defined(OS_ANDROID)
     // TODO(bauerb): Get rid of the platform-specific #ifdef here.
     // http://crbug.com/313377
     BrowserList::AddObserver(this);
 #endif
@@ skipping 118 matching lines @@
   // The active user can be NULL in unit tests.
   if (user_manager::UserManager::Get()->GetActiveUser()) {
     return UTF16ToUTF8(user_manager::UserManager::Get()->GetUserDisplayName(
         user_manager::UserManager::Get()->GetActiveUser()->GetUserID()));
   }
   return std::string();
 #else
   return profile_->GetPrefs()->GetString(prefs::kProfileName);
 #endif
 }