Add histogram to track prerender sessions

chrome/browser/prerender/prerender_manager.cc

 // Copyright (c) 2010 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_manager.h"
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_thread.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/browser/tab_contents/render_view_host_manager.h"
 #include "chrome/common/render_messages.h"
 
+// static
+PrerenderManager::PrerenderManagerMode PrerenderManager::mode_ =
+    PRERENDER_MODE_ENABLED;
+
+// static
+PrerenderManager::PrerenderManagerMode PrerenderManager::GetMode() {
+  return mode_;
+}
+
+// static
+void PrerenderManager::SetMode(PrerenderManagerMode mode) {
+  mode_ = mode;
+}
+
 struct PrerenderManager::PrerenderContentsData {
   PrerenderContents* contents_;
   base::Time start_time_;
   GURL url_;
   PrerenderContentsData(PrerenderContents* contents,
                         base::Time start_time,
                         GURL url)
       : contents_(contents),
         start_time_(start_time),
         url_(url) {
   }
 };
 
 PrerenderManager::PrerenderManager(Profile* profile)
     : profile_(profile),
       max_prerender_age_(base::TimeDelta::FromSeconds(
           kDefaultMaxPrerenderAgeSeconds)),
       max_elements_(kDefaultMaxPrerenderElements),
-      prerender_contents_factory_(PrerenderContents::CreateFactory()),
-      mode_(PRERENDER_MODE_ENABLED) {
+      prerender_contents_factory_(PrerenderContents::CreateFactory()) {
 }
 
 PrerenderManager::~PrerenderManager() {
   while (prerender_list_.size() > 0) {
     PrerenderContentsData data = prerender_list_.front();
     prerender_list_.pop_front();
     delete data.contents_;
   }
 }
 
@@ skipping 99 matching lines @@
 }
 
 PrerenderContents* PrerenderManager::CreatePrerenderContents(
     const GURL& url,
     const std::vector<GURL>& alias_urls) {
   return prerender_contents_factory_->CreatePrerenderContents(
       this, profile_, url, alias_urls);
 }
 
 void PrerenderManager::RecordPerceivedPageLoadTime(base::TimeDelta pplt) {
-  switch(mode_) {
+  switch (mode_) {
     case PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP:
       UMA_HISTOGRAM_TIMES("PLT.PerceivedPageLoadTime_PrerenderControl", pplt);
       break;
     case PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP:
       UMA_HISTOGRAM_TIMES("PLT.PerceivedPageLoadTime_PrerenderTreatment", pplt);
       break;
     default:
       break;
   }
 }
 
 PrerenderContents* PrerenderManager::FindEntry(const GURL& url) {
   for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
        it != prerender_list_.end();
        ++it) {
     if (it->contents_->MatchesURL(url))
       return it->contents_;
   }
   // Entry not found.
   return NULL;
 }