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

chrome/browser/prerender/prerender_histograms.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_histograms.h"
 
 #include <string>
 
+#include "base/format_macros.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/predictors/autocomplete_action_predictor.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_util.h"
 
 using predictors::AutocompleteActionPredictor;
 
@@ skipping 131 matching lines @@
 
 void PrerenderHistograms::RecordPrerenderStarted(Origin origin) const {
   if (OriginIsOmnibox(origin)) {
     UMA_HISTOGRAM_COUNTS(
         StringPrintf("Prerender.OmniboxPrerenderCount%s",
                      PrerenderManager::GetModeString()).c_str(),
         1);
   }
 }
 
+void PrerenderHistograms::RecordConcurrency(size_t prerender_count) const {
+  const size_t max_concurrency = PrerenderManager::GetMaxConcurrency();
+  if (max_concurrency > 1) {
+    UMA_HISTOGRAM_ENUMERATION(
+        StringPrintf("Prerender.PrerenderCountOf%" PRIuS "Max",
+                     max_concurrency),
+        prerender_count, Config::kMaximumMaxConcurrency + 1);
+  }
+}
+
+
 void PrerenderHistograms::RecordUsedPrerender(Origin origin) const {
   if (OriginIsOmnibox(origin)) {
     UMA_HISTOGRAM_COUNTS(
         StringPrintf("Prerender.OmniboxNavigationsUsedPrerenderCount%s",
                      PrerenderManager::GetModeString()).c_str(),
         1);
   }
 }
 
 void PrerenderHistograms::RecordTimeSinceLastRecentVisit(
@@ skipping 234 matching lines @@
       "LocalPredictorTimeUntilUsed",
       UMA_HISTOGRAM_CUSTOM_TIMES(
           name,
           time_until_used,
           base::TimeDelta::FromMilliseconds(10),
           max_age,
           50));
 }
 
 }  // namespace prerender