[net] Re-enable async DNS field trial (on canary only)

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 "build/build_config.h"
 #include "chrome/common/chrome_version_info.h"
 
 namespace chrome_browser_net {
 
 bool ConfigureAsyncDnsFieldTrial() {
 #if defined(OS_ANDROID) || defined(OS_IOS) || defined(OS_CHROMEOS)
   // 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;
 
-  // TODO(szym): bring the probability up after fixing http://crbug.com/121085
-  if (chrome::VersionInfo::GetChannel() <= chrome::VersionInfo::CHANNEL_DEV)
-    enabled_probability = 0;
+  // TODO(szym): expand to DEV channel after fixing http://crbug.com/121085
+  if (chrome::VersionInfo::GetChannel() <= chrome::VersionInfo::CHANNEL_CANARY)
+    enabled_probability = 50;
 
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
           "AsyncDns", kAsyncDnsDivisor, "disabled", 2012, 9, 30, NULL));
 
   int enabled_group = trial->AppendGroup("enabled", enabled_probability);
   return trial->group() == enabled_group;
 }
 
 }  // namespace chrome_browser_net