Move AsyncDns field trial to server-side control.

chrome/browser/net/async_dns_field_trial.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/net/async_dns_field_trial.h"
 
 #include "base/metrics/field_trial.h"
+#include "base/string_util.h"
 #include "build/build_config.h"
-#include "chrome/common/chrome_version_info.h"
 
 namespace chrome_browser_net {
 
 bool ConfigureAsyncDnsFieldTrial() {
 #if defined(OS_ANDROID) || defined(OS_IOS)
   // There is no DnsConfigService on those platforms so disable the field trial.
   return false;
 #endif
-  const base::FieldTrial::Probability kAsyncDnsDivisor = 100;
-  base::FieldTrial::Probability enabled_probability = 0;
-
-  if (chrome::VersionInfo::GetChannel() <= chrome::VersionInfo::CHANNEL_DEV)
-    enabled_probability = 50;
-
-  scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial(
-          "AsyncDns", kAsyncDnsDivisor, "disabled", 2012, 10, 30, NULL));
-
-  int enabled_group = trial->AppendGroup("enabled", enabled_probability);
-  return trial->group() == enabled_group;
+  // Match both "AsyncDnsA" and "AsyncDnsB" groups.
+  return StartsWithASCII(base::FieldTrialList::FindFullName("AsyncDns"),
+                         "AsyncDns", false /* case_sensitive */);
 }
 
 }  // namespace chrome_browser_net