Make three simultanious prerenders the default maximum in Canary and Dev only.

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 a8e8991df723ba631ba9a38eafab797e3f0d6f3a..be1e1ae5cd05a25feb4733a758e7de78b84f1afe 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -48,32 +48,37 @@ void SetupPrefetchFieldTrial() {
 void SetupPrerenderFieldTrial() {
   base::FieldTrial::Probability divisor = 1000;
 
-  base::FieldTrial::Probability exp1_probability = 166;
-  base::FieldTrial::Probability exp1_5min_ttl_probability = 83;
-  base::FieldTrial::Probability control1_probability = 166;
-  base::FieldTrial::Probability no_use1_probability = 83;
-
-  base::FieldTrial::Probability exp2_probability = 167;
-  base::FieldTrial::Probability exp2_5min_ttl_probability = 84;
-  base::FieldTrial::Probability control2_probability = 167;
-  base::FieldTrial::Probability no_use2_probability = 84;
+  base::FieldTrial::Probability exp1_probability = 150;

[dominich, 2012/07/19 16:04:38]

I would very much like to remove half of these now that we're confident that
variance within each group is within acceptable bounds.

[gavinp, 2012/07/23 18:35:21]

I like that plan, but I figured a separate CL for cleaning this up makes more
sense. See http://codereview.chromium.org/10802062/ , which my upload rebases
on.

+  base::FieldTrial::Probability exp1_5min_ttl_probability = 67;
+  base::FieldTrial::Probability control1_probability = 150;
+  base::FieldTrial::Probability no_use1_probability = 67;
+  base::FieldTrial::Probability one_prerender1_probability = 66;

[dominich, 2012/07/19 16:04:38]

We should flip this around. have exp[12] be single prerender as it is now, and
add an experiment for multiple prerenders.

[gavinp, 2012/07/23 18:35:21]

Done.

+
+  base::FieldTrial::Probability exp2_probability = 150;
+  base::FieldTrial::Probability exp2_5min_ttl_probability = 67;
+  base::FieldTrial::Probability control2_probability = 150;
+  base::FieldTrial::Probability no_use2_probability = 67;
+  base::FieldTrial::Probability one_prerender2_probability = 66;
 
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
       channel == chrome::VersionInfo::CHANNEL_BETA) {
-    exp1_probability = 490;
+    exp1_probability = 0;
     exp1_5min_ttl_probability = 5;
     control1_probability = 5;
     no_use1_probability = 0;
-    exp2_probability = 490;
+    one_prerender1_probability = 490;
+    exp2_probability = 0;
     exp2_5min_ttl_probability = 5;
     control2_probability = 5;
     no_use2_probability = 0;
+    one_prerender2_probability = 490;
   }
   CHECK_EQ(divisor, exp1_probability + exp1_5min_ttl_probability +
-           control1_probability + no_use1_probability + exp2_probability +
+           control1_probability + no_use1_probability +
+           one_prerender1_probability + exp2_probability +
            exp2_5min_ttl_probability + control2_probability +
-           no_use2_probability);
+           no_use2_probability + one_prerender2_probability);
   int experiment_1_group = -1;
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
@@ -89,6 +94,9 @@ void SetupPrerenderFieldTrial() {
   const int no_use_1_group =
       trial->AppendGroup("ContentPrefetchPrerenderNoUse1",
                          no_use1_probability);
+  const int one_prerender_1_group =
+      trial->AppendGroup("ContentPrefetchPrerenderOne",
+                         one_prerender1_probability);
   const int experiment_2_group =
       trial->AppendGroup("ContentPrefetchPrerender2",
                          exp2_probability);
@@ -101,6 +109,9 @@ void SetupPrerenderFieldTrial() {
   const int no_use_2_group =
       trial->AppendGroup("ContentPrefetchPrerenderNoUse2",
                          no_use2_probability);
+  const int one_prerender_2_group =
+      trial->AppendGroup("ContentPrefetchPrerenderOne",
+                         one_prerender2_probability);
   const int trial_group = trial->group();
   if (trial_group == experiment_1_group ||
       trial_group == experiment_2_group) {
@@ -118,6 +129,10 @@ void SetupPrerenderFieldTrial() {
              trial_group == no_use_2_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP);
+  } else if (trial_group == one_prerender_1_group ||
+             trial_group == one_prerender_2_group) {
+    PrerenderManager::SetMode(
+        PrerenderManager::PRERENDER_MODE_EXPERIMENT_ONE_PRERENDER_GROUP);
   } else {
     NOTREACHED();
   }