Add histogram to track prerender sessions

BUG=70401
TEST=nope

Review URL: http://codereview.chromium.org/6340013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72800 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 41 insertions, 9 deletions

diff --git a/chrome/browser/browser_main.cc b/chrome/browser/browser_main.cc
index df290e3..f937f3f 100644
--- a/chrome/browser/browser_main.cc
+++ b/chrome/browser/browser_main.cc
@@ -56,6 +56,7 @@
 #include "chrome/browser/prefs/browser_prefs.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/pref_value_store.h"
+#include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/printing/cloud_print/cloud_print_proxy_service.h"
 #include "chrome/browser/printing/print_dialog_cloud.h"
 #include "chrome/browser/process_singleton.h"
@@ -224,7 +225,7 @@ void BrowserMainParts::SetupFieldTrials() {
   ConnectionFieldTrial();
   SocketTimeoutFieldTrial();
   ProxyConnectionsFieldTrial();
-  PrefetchFieldTrial();
+  PrefetchAndPrerenderFieldTrial();
   SpdyFieldTrial();
   ConnectBackupJobsFieldTrial();
 }
@@ -429,7 +430,7 @@ void BrowserMainParts::SpdyFieldTrial() {
 // --disable-content-prefetch are set, use those to determine if
 // prefetch is enabled. Otherwise, randomly assign users to an A/B test for
 // prefetching.
-void BrowserMainParts::PrefetchFieldTrial() {
+void BrowserMainParts::PrefetchAndPrerenderFieldTrial() {
   if (parsed_command_line().HasSwitch(switches::kEnableContentPrefetch) ||
       parsed_command_line().HasSwitch(switches::kEnablePagePrerender))
     ResourceDispatcherHost::set_is_prefetch_enabled(true);
@@ -448,6 +449,17 @@ void BrowserMainParts::PrefetchFieldTrial() {
     ResourceDispatcherHost::set_is_prefetch_enabled(
         trial_grp == yes_prefetch_grp);
   }
+
+  PrerenderManager::PrerenderManagerMode prerender_mode =
+      PrerenderManager::PRERENDER_MODE_DISABLED;
+  if (parsed_command_line().HasSwitch(switches::kEnablePagePrerender))
+    prerender_mode = PrerenderManager::PRERENDER_MODE_ENABLED;
+  else
+    prerender_mode = PrerenderManager::PRERENDER_MODE_DISABLED;
+  PrerenderManager::SetMode(prerender_mode);
+
+  UMA_HISTOGRAM_ENUMERATION("Prerender.Sessions", prerender_mode,
+                            PrerenderManager::PRERENDER_MODE_MAX);
 }
 
 // If neither --enable-connect-backup-jobs or --disable-connect-backup-jobs is
diff --git a/chrome/browser/browser_main.h b/chrome/browser/browser_main.h
index a8f5442..1c0b3711c 100644
--- a/chrome/browser/browser_main.h
+++ b/chrome/browser/browser_main.h
@@ -118,8 +118,9 @@ class BrowserMainParts {
   // A/B test for spdy when --use-spdy not set.
   void SpdyFieldTrial();
 
-  // A/B test for prefetching with --(enable|disable)-prefetch not set.
-  void PrefetchFieldTrial();
+  // A/B test for prefetching with --(enable|disable)-prefetch not set,
+  // some histograms tracking prerender sessions.
+  void PrefetchAndPrerenderFieldTrial();
 
   // A/B test for automatically establishing a backup TCP connection when a
   // specified timeout value is reached.
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index 0459058..9b90ef88 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -15,6 +15,20 @@
 #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_;
@@ -33,8 +47,7 @@ PrerenderManager::PrerenderManager(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() {
@@ -154,7 +167,7 @@ PrerenderContents* PrerenderManager::CreatePrerenderContents(
 }
 
 void PrerenderManager::RecordPerceivedPageLoadTime(base::TimeDelta pplt) {
-  switch(mode_) {
+  switch (mode_) {
     case PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP:
       UMA_HISTOGRAM_TIMES("PLT.PerceivedPageLoadTime_PrerenderControl", pplt);
       break;
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index 62967d8..bb65b44 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -22,11 +22,14 @@ class TabContents;
 // views of webpages.
 class PrerenderManager : public base::RefCounted<PrerenderManager> {
  public:
+  // PrerenderManagerMode is used in a UMA_HISTOGRAM, so please do not
+  // add in the middle.
   enum PrerenderManagerMode {
     PRERENDER_MODE_DISABLED,
     PRERENDER_MODE_ENABLED,
     PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP,
-    PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP
+    PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP,
+    PRERENDER_MODE_MAX
   };
 
   // Owned by a Profile object for the lifetime of the profile.
@@ -59,6 +62,9 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
   unsigned int max_elements() const { return max_elements_; }
   void set_max_elements(unsigned int num) { max_elements_ = num; }
 
+  static PrerenderManagerMode GetMode();
+  static void SetMode(PrerenderManagerMode mode);
+
  protected:
   virtual ~PrerenderManager();
 
@@ -100,7 +106,7 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
 
   scoped_ptr<PrerenderContents::Factory> prerender_contents_factory_;
 
-  PrerenderManagerMode mode_;
+  static PrerenderManagerMode mode_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };