Add field trial to extend prerender expiration to 5 minutes.

chrome/browser/prerender/prerender_field_trial.cc

Index: chrome/browser/prerender/prerender_field_trial.cc
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index e5174b6eaa804326158fe81667d97362dae5c220..f6546393c67cb4452e595482f99750639499333f 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -42,31 +42,42 @@ void SetupPrefetchFieldTrial() {
 }
 
 void SetupPrerenderFieldTrial() {
-  base::FieldTrial::Probability divisor = 1000;
+  base::FieldTrial::Probability divisor = 1200;
+
   base::FieldTrial::Probability exp1_probability = 200;
+  base::FieldTrial::Probability exp1_long_ttl_probability = 100;
   base::FieldTrial::Probability control1_probability = 200;
   base::FieldTrial::Probability no_use1_probability = 100;
+
   base::FieldTrial::Probability exp2_probability = 200;
+  base::FieldTrial::Probability exp2_long_ttl_probability = 100;
   base::FieldTrial::Probability control2_probability = 200;
   base::FieldTrial::Probability no_use2_probability = 100;
+
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
       channel == chrome::VersionInfo::CHANNEL_BETA) {
-    exp1_probability = 495;
+    exp1_probability = 490;

[cbentzel, 2012/02/27 19:23:20]

These no longer sum to 1200

[dominich, 2012/02/27 19:29:53]

Nice catch - that would have been a release check fail in beta.

Maybe we should extract the stable/beta constants from the dev constants and do
two checks to ensure the sums are correct.

+    exp1_long_ttl_probability = 5;
     control1_probability = 5;
     no_use1_probability = 0;
-    exp2_probability = 495;
+    exp2_probability = 490;
+    exp2_long_ttl_probability = 5;
     control2_probability = 5;
     no_use2_probability = 0;
   }
-  CHECK_EQ(divisor, exp1_probability + control1_probability +
-           no_use1_probability + exp2_probability +
-           control2_probability + no_use2_probability);
+  CHECK_EQ(divisor, exp1_probability + exp1_long_ttl_probability +
+           control1_probability + no_use1_probability + exp2_probability +
+           exp2_long_ttl_probability + control2_probability +
+           no_use2_probability);
   scoped_refptr<base::FieldTrial> trial(
       new base::FieldTrial("Prerender", divisor,
                            "ContentPrefetchPrerender1", 2012, 6, 30));
 
   const int kExperiment1Group = trial->kDefaultGroupNumber;
+  const int kExperiment1LongTTLGroup =
+      trial->AppendGroup("ContentPrefetchPrerenderExpLongTTL1",
+                         exp1_long_ttl_probability);
   const int kControl1Group =
       trial->AppendGroup("ContentPrefetchPrerenderControl1",
                          control1_probability);
@@ -76,6 +87,9 @@ void SetupPrerenderFieldTrial() {
   const int kExperiment2Group =
       trial->AppendGroup("ContentPrefetchPrerender2",
                          exp2_probability);
+  const int kExperiment2LongTTLGroup =
+      trial->AppendGroup("ContentPrefetchPrerenderExpLongTTL2",
+                         exp2_long_ttl_probability);
   const int kControl2Group =
       trial->AppendGroup("ContentPrefetchPrerenderControl2",
                          control2_probability);
@@ -87,6 +101,10 @@ void SetupPrerenderFieldTrial() {
       trial_group == kExperiment2Group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP);
+  } else if (trial_group == kExperiment1LongTTLGroup ||
+             trial_group == kExperiment2LongTTLGroup) {
+    PrerenderManager::SetMode(
+        PrerenderManager::PRERENDER_MODE_EXPERIMENT_LONG_TTL_GROUP);
   } else if (trial_group == kControl1Group ||
              trial_group == kControl2Group) {
     PrerenderManager::SetMode(