[net] Add AsyncDns field trial.

chrome/test/base/test_launcher_utils.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/test/base/test_launcher_utils.h"
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 10 matching lines @@
 namespace test_launcher_utils {
 
 void PrepareBrowserCommandLineForTests(CommandLine* command_line) {
   // Turn off tip loading for tests; see http://crbug.com/17725.
   command_line->AppendSwitch(switches::kDisableWebResources);
 
   // Turn off preconnects because they break the brittle python webserver;
   // see http://crbug.com/60035.
   command_line->AppendSwitch(switches::kDisablePreconnect);
 
+  // Turn off built-in asynchronous DNS client.
+  command_line->AppendSwitch(switches::kDisableAsyncDns);
+
   // Don't show the first run ui.
   command_line->AppendSwitch(switches::kNoFirstRun);
 
   // No default browser check, it would create an info-bar (if we are not the
   // default browser) that could conflicts with some tests expectations.
   command_line->AppendSwitch(switches::kNoDefaultBrowserCheck);
 
   // Enable warning level logging so that we can see when bad stuff happens.
   command_line->AppendSwitch(switches::kEnableLogging);
   command_line->AppendSwitchASCII(switches::kLoggingLevel, "1");  // warning
@@ skipping 56 matching lines @@
                               const std::string& implementation_name) {
   if (command_line->HasSwitch(switches::kUseGL))
     return false;
 
   command_line->AppendSwitchASCII(switches::kUseGL, implementation_name);
 
   return true;
 }
 
 }  // namespace test_launcher_utils