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 1d48b471cbd12ca3305c8d3ba14b9cab64eccfd9..60ce6a39ea56387a150ff6f0ce78f38c2d13055e 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -52,6 +52,7 @@ void SetupPrerenderFieldTrial() {
   const FieldTrial::Probability divisor = 1000;
 
   FieldTrial::Probability control_probability;
+  FieldTrial::Probability experiment_multi_prerender_probability;
   FieldTrial::Probability experiment_5min_ttl_probability;
   FieldTrial::Probability experiment_no_use_probability;
 
@@ -61,30 +62,40 @@ void SetupPrerenderFieldTrial() {
     // Use very conservatives and stable settings in beta and stable.
     const FieldTrial::Probability release_prerender_enabled_probability = 980;
     const FieldTrial::Probability release_control_probability = 10;
+    const FieldTrial::Probability
+        release_experiment_multi_prerender_probability = 0;
     const FieldTrial::Probability release_experiment_5min_ttl_probability = 10;
     const FieldTrial::Probability release_experiment_no_use_probability = 0;
     COMPILE_ASSERT(
         release_prerender_enabled_probability + release_control_probability +
+        release_experiment_multi_prerender_probability +
         release_experiment_5min_ttl_probability +
         release_experiment_no_use_probability == divisor,
         release_experiment_probabilities_must_equal_divisor);
 
     control_probability = release_experiment_5min_ttl_probability;
+    experiment_multi_prerender_probability =
+        release_experiment_multi_prerender_probability;
     experiment_5min_ttl_probability = release_control_probability;
     experiment_no_use_probability = release_experiment_no_use_probability;
   } else {
     // In testing channels, use more experiments and a larger control group to
     // improve quality of data.
-    const FieldTrial::Probability dev_prerender_enabled_probability = 333;
-    const FieldTrial::Probability dev_control_probability = 333;
-    const FieldTrial::Probability dev_experiment_5min_ttl_probability = 167;
-    const FieldTrial::Probability dev_experiment_no_use_probability = 167;
+    const FieldTrial::Probability dev_prerender_enabled_probability = 250;
+    const FieldTrial::Probability dev_control_probability = 250;
+    const FieldTrial::Probability
+        dev_experiment_multi_prerender_probability = 250;
+    const FieldTrial::Probability dev_experiment_5min_ttl_probability = 125;
+    const FieldTrial::Probability dev_experiment_no_use_probability = 125;
     COMPILE_ASSERT(dev_prerender_enabled_probability + dev_control_probability +
+                   dev_experiment_multi_prerender_probability +
                    dev_experiment_5min_ttl_probability +
                    dev_experiment_no_use_probability == divisor,
                    dev_experiment_probabilities_must_equal_divisor);
 
     control_probability = dev_experiment_5min_ttl_probability;
+    experiment_multi_prerender_probability =
+        dev_experiment_multi_prerender_probability;
     experiment_5min_ttl_probability = dev_control_probability;
     experiment_no_use_probability = dev_experiment_no_use_probability;
   }
@@ -97,6 +108,9 @@ void SetupPrerenderFieldTrial() {
   const int control_group =
       trial->AppendGroup("PrerenderControl",
                          control_probability);
+  const int experiment_multi_prerender_group =
+      trial->AppendGroup("PrerenderMulti",
+                         experiment_multi_prerender_probability);
   const int experiment_5_min_TTL_group =
       trial->AppendGroup("Prerender5minTTL",
                          experiment_5min_ttl_probability);
@@ -111,6 +125,9 @@ void SetupPrerenderFieldTrial() {
   } else if (trial_group == control_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP);
+  } else if (trial_group == experiment_multi_prerender_group) {
+    PrerenderManager::SetMode(
+        PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP);
   } else if (trial_group == experiment_5_min_TTL_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP);