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/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
@@ skipping 130 matching lines @@
   last_experiment_id_ = experiment;
 
   // If we observe multiple tags within the 30 second window, we will still
   // reset the window to begin at the most recent occurrence, so that we will
   // always be in a window in the 30 seconds from each occurrence.
   last_prerender_seen_time_ = GetCurrentTimeTicks();
   seen_any_pageload_ = false;
   seen_pageload_started_after_prerender_ = false;
 }
 
-void PrerenderHistograms::RecordPrerenderStarted(Origin origin) const {
+void PrerenderHistograms::RecordPrerenderStarted(Origin origin,
+                                                 size_t prerender_count) const {
+  UMA_HISTOGRAM_ENUMERATION("Prerender.PrerenderCount", prerender_count,
+                            Config::kDefaultMaxConcurrency + 1);

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

this will be a measure of how often we prerender 1 vs 2 (vs ?) prererenders
concurrently? Does this number then need to be modulated by experiment, ie,
should we only record this for the experiment where maximum concurrency is > 1?
Or, even better, add a separate histogram for each maximum concurrency:

StringPrintf("Prerender.ConcurrentPrerenderCount%d",
PrerenderManager::config().concurrency)

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

Good idea: I now only emit this if the max concurrency > 1. I also added the
integer to the name.

   if (OriginIsOmnibox(origin)) {
     UMA_HISTOGRAM_COUNTS(
         StringPrintf("Prerender.OmniboxPrerenderCount%s",
                      PrerenderManager::GetModeString()).c_str(),
         1);
   }
 }
 
 void PrerenderHistograms::RecordUsedPrerender(Origin origin) const {
   if (OriginIsOmnibox(origin)) {
@@ skipping 242 matching lines @@
       "LocalPredictorTimeUntilUsed",
       UMA_HISTOGRAM_CUSTOM_TIMES(
           name,
           time_until_used,
           base::TimeDelta::FromMilliseconds(10),
           max_age,
           50));
 }
 
 }  // namespace prerender