Do conservative prerendering based on the LocalPredictor in Dev/Canary.

chrome/browser/prerender/prerender_field_trial.cc

Index: chrome/browser/prerender/prerender_field_trial.cc
===================================================================
--- chrome/browser/prerender/prerender_field_trial.cc	(revision 198752)
+++ chrome/browser/prerender/prerender_field_trial.cc	(working copy)
@@ -28,6 +28,7 @@
 
 const char kLocalPredictorTrialName[] = "PrerenderLocalPredictor";
 const char kLocalPredictorEnabledGroup[] = "Enabled";
+const char kLocalPredictorDisabledGroup[] = "Disabled";
 
 const char kLoggedInPredictorTrialName[] = "PrerenderLoggedInPredictor";
 const char kLoggedInPredictorEnabledGroup[] = "Enabled";
@@ -149,6 +150,7 @@
 }  // end namespace
 
 void ConfigureOmniboxPrerender();
+void ConfigureLocalPredictor();
 void ConfigureLoggedInPredictor();
 void ConfigureSideEffectFreeWhitelist();
 
@@ -207,6 +209,7 @@
   }
 
   ConfigureOmniboxPrerender();
+  ConfigureLocalPredictor();
   ConfigureLoggedInPredictor();
   ConfigureSideEffectFreeWhitelist();
 }
@@ -229,6 +232,19 @@
                                        kDisabledProbability);
 }
 
+void ConfigureLocalPredictor() {
+  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();

[Shishir, 2013/05/07 22:57:30]

Since this can have bad side effects there should be a way for users to turn
this off on the dev channel. Add a flag in about:flags?

[tburkard, 2013/05/07 23:21:59]

I will do this separately (before committing), but wanted to send out these
comments to you first.

+  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
+      channel == chrome::VersionInfo::CHANNEL_BETA) {
+    return;
+  }
+  scoped_refptr<FieldTrial> local_predictor_trial(
+      FieldTrialList::FactoryGetFieldTrial(
+          kLocalPredictorTrialName, 100,
+          kLocalPredictorDisabledGroup, 2013, 12, 31, NULL));
+  local_predictor_trial->AppendGroup(kLocalPredictorEnabledGroup, 100);
+}
+
 void ConfigureLoggedInPredictor() {
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_STABLE ||