Feature to disable field trials in old versions of Chromium. Field trials...

chrome/browser/net/predictor_api.cc

Index: chrome/browser/net/predictor_api.cc
===================================================================
--- chrome/browser/net/predictor_api.cc	(revision 71223)
+++ chrome/browser/net/predictor_api.cc	(working copy)
@@ -551,13 +551,15 @@
   // For each option (i.e., non-default), we have a fixed probability.
   base::FieldTrial::Probability kProbabilityPerGroup = 100;  // 10% probability.
 
-  trial_ = new base::FieldTrial("DnsImpact", kDivisor);
+  // After June 30, 2011 builds, it will always be in defaut group
+  // (default_enabled_prefetch).
+  trial_ = new base::FieldTrial("DnsImpact", kDivisor,
+                                "default_enabled_prefetch", 2011, 6, 30);
 
   // First option is to disable prefetching completely.
   int disabled_prefetch = trial_->AppendGroup("disabled_prefetch",
                                               kProbabilityPerGroup);
 
-
   // We're running two experiments at the same time.  The first set of trials
   // modulates the delay-time until we declare a congestion event (and purge
   // our queue).  The second modulates the number of concurrent resolutions
@@ -586,9 +588,6 @@
   int max_6_concurrent_prefetch = trial_->AppendGroup(
       "max_6 concurrent_prefetch", kProbabilityPerGroup);
 
-  trial_->AppendGroup("default_enabled_prefetch",
-      base::FieldTrial::kAllRemainingProbability);
-
   // We will register the incognito observer regardless of whether prefetching
   // is enabled, as it is also used to clear the host cache.
   g_off_the_record_observer.Get().Register();