Avoid doing periodic prerender cleanup when there are no contents.

chrome/browser/prerender/prerender_field_trial.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prerender/prerender_field_trial.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
@@ skipping 72 matching lines @@
     "DisableSessionStorageNamespaceMerging";
 const char kPrerenderCookieStore[] = "PrerenderCookieStore";
 
 void SetupPrerenderFieldTrial() {
   const FieldTrial::Probability divisor = 1000;
 
   FieldTrial::Probability control_probability;
   FieldTrial::Probability experiment_multi_prerender_probability;
   FieldTrial::Probability experiment_15min_ttl_probability;
   FieldTrial::Probability experiment_no_use_probability;
+  FieldTrial::Probability experiment_match_complete_probability;
 
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
       channel == chrome::VersionInfo::CHANNEL_BETA) {
     // Use very conservatives and stable settings in beta and stable.
-    const FieldTrial::Probability release_prerender_enabled_probability = 980;
+    const FieldTrial::Probability release_prerender_enabled_probability = 970;
     const FieldTrial::Probability release_control_probability = 10;
     const FieldTrial::Probability
         release_experiment_multi_prerender_probability = 0;
     const FieldTrial::Probability release_experiment_15min_ttl_probability = 10;
     const FieldTrial::Probability release_experiment_no_use_probability = 0;
+    const FieldTrial::Probability
+        release_experiment_match_complete_probability = 10;
     COMPILE_ASSERT(
-        release_prerender_enabled_probability + release_control_probability +
+        release_prerender_enabled_probability +
+        release_control_probability +
         release_experiment_multi_prerender_probability +
         release_experiment_15min_ttl_probability +
-        release_experiment_no_use_probability == divisor,
+        release_experiment_no_use_probability +
+        release_experiment_match_complete_probability == divisor,
         release_experiment_probabilities_must_equal_divisor);
 
     control_probability = release_control_probability;
     experiment_multi_prerender_probability =
         release_experiment_multi_prerender_probability;
     experiment_15min_ttl_probability = release_experiment_15min_ttl_probability;
     experiment_no_use_probability = release_experiment_no_use_probability;
+    experiment_match_complete_probability =
+        release_experiment_match_complete_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 = 250;
     const FieldTrial::Probability dev_control_probability = 250;
     const FieldTrial::Probability
-        dev_experiment_multi_prerender_probability = 250;
-    const FieldTrial::Probability dev_experiment_15min_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 = 200;
+    const FieldTrial::Probability dev_experiment_15min_ttl_probability = 100;
+    const FieldTrial::Probability dev_experiment_no_use_probability = 100;
+    const FieldTrial::Probability
+        dev_experiment_match_complete_probability = 100;

[tburkard, 2014/09/17 09:23:20]

It's best if the #'s are the same, for easier comparison.
I would prefer:
Enabled=200
Control=200
Multi=200
15min=100
nouse=100
MatchComplete=200

Thanks.

+    COMPILE_ASSERT(dev_prerender_enabled_probability +
+                   dev_control_probability +
                    dev_experiment_multi_prerender_probability +
                    dev_experiment_15min_ttl_probability +
-                   dev_experiment_no_use_probability == divisor,
+                   dev_experiment_no_use_probability +
+                   dev_experiment_match_complete_probability == divisor,
                    dev_experiment_probabilities_must_equal_divisor);
 
     control_probability = dev_control_probability;
     experiment_multi_prerender_probability =
         dev_experiment_multi_prerender_probability;
     experiment_15min_ttl_probability = dev_experiment_15min_ttl_probability;
     experiment_no_use_probability = dev_experiment_no_use_probability;
+    experiment_match_complete_probability =
+        dev_experiment_match_complete_probability;
   }
 
   int prerender_enabled_group = -1;
   scoped_refptr<FieldTrial> trial(
       FieldTrialList::FactoryGetFieldTrial(
           "Prerender", divisor, "PrerenderEnabled",
           2014, 12, 31, FieldTrial::SESSION_RANDOMIZED,
           &prerender_enabled_group));
   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_15_min_TTL_group =
       trial->AppendGroup("Prerender15minTTL",
                          experiment_15min_ttl_probability);
   const int experiment_no_use_group =
       trial->AppendGroup("PrerenderNoUse",
                          experiment_no_use_probability);
+  const int experiment_match_complete_group =
+      trial->AppendGroup("MatchComplete",
+                         experiment_match_complete_probability);
 
   const int trial_group = trial->group();
   if (trial_group == prerender_enabled_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP);
   } 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_15_min_TTL_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP);
   } else if (trial_group == experiment_no_use_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP);
+  } else if (trial_group == experiment_match_complete_group) {
+    PrerenderManager::SetMode(
+        PrerenderManager::PRERENDER_MODE_EXPERIMENT_MATCH_COMPLETE_GROUP);
   } else {
     NOTREACHED();
   }
 }
 
 }  // end namespace
 
 void ConfigureOmniboxPrerender();
 
 void ConfigurePrerender(const CommandLine& command_line) {
@@ skipping 281 matching lines @@
   return GetLocalPredictorSpecValue(kDisableSessionStorageNamespaceMerging) !=
       kDisabledGroup;
 }
 
 bool IsPrerenderCookieStoreEnabled() {
   return GetLocalPredictorSpecValue(kPrerenderCookieStore) != kDisabledGroup &&
       FieldTrialList::FindFullName(kPrerenderCookieStore) != kDisabledGroup;
 }
 
 }  // namespace prerender