1 files changed, 57 insertions, 0 deletions

diff --git a/chrome/renderer/page_load_histograms.cc b/chrome/renderer/page_load_histograms.cc
index 48ef7e5..3603981 100644
--- a/chrome/renderer/page_load_histograms.cc
+++ b/chrome/renderer/page_load_histograms.cc
@@ -28,6 +28,54 @@ static const size_t kPLTCount(100);
 #define PLT_HISTOGRAM(name, sample) \
     UMA_HISTOGRAM_CUSTOM_TIMES(name, sample, kPLTMin, kPLTMax, kPLTCount);
 
+namespace {
+
+// Histograms to determine prerendering's impact on perceived PLT.
+void UpdatePrerenderHistograms(NavigationState* navigation_state,
+                               const Time& begin, const Time& finish_all_loads,
+                               const TimeDelta& begin_to_finish_all_loads) {
+  // Load time for non-prerendered pages.
+  static bool use_prerender_histogram =
+      base::FieldTrialList::Find("Prerender") &&
+      !base::FieldTrialList::Find("Prerender")->group_name().empty();
+  if (!navigation_state->was_started_as_prerender()) {
+    if (use_prerender_histogram) {
+      PLT_HISTOGRAM(base::FieldTrial::MakeName(
+          "PLT.PerceivedLoadTime", "Prerender"),
+          begin_to_finish_all_loads);
+    }
+    return;
+  }
+
+  // Histogram for usage rate of prerendered pages.
+  Time prerendered_page_display =
+      navigation_state->prerendered_page_display_time();
+  UMA_HISTOGRAM_ENUMERATION("PLT.PageUsed_PrerenderLoad",
+                            prerendered_page_display.is_null() ? 0 : 1, 2);
+  if (prerendered_page_display.is_null())
+    return;
+
+  // Histograms for perceived load time of prerendered pages.
+  PLT_HISTOGRAM("PLT.TimeUntilDisplay_PrerenderLoad",
+                prerendered_page_display - begin);
+  TimeDelta perceived_load_time = finish_all_loads - prerendered_page_display;
+  if (perceived_load_time < TimeDelta::FromSeconds(0)) {
+    PLT_HISTOGRAM("PLT.PrerenderIdleTime_PrerenderLoad", -perceived_load_time);
+    perceived_load_time = TimeDelta::FromSeconds(0);
+  }
+  PLT_HISTOGRAM("PLT.PerceivedLoadTime_PrerenderLoad", perceived_load_time);
+  if (use_prerender_histogram) {
+    PLT_HISTOGRAM(base::FieldTrial::MakeName(
+                  "PLT.PerceivedLoadTime_PrerenderLoad", "Prerender"),
+                  perceived_load_time);
+    PLT_HISTOGRAM(base::FieldTrial::MakeName(
+                  "PLT.PerceivedLoadTime", "Prerender"),
+                  perceived_load_time);
+  }
+}
+
+}  // namespace
+
 // Returns the scheme type of the given URL if its type is one for which we
 // dump page load histograms. Otherwise returns NULL.
 static URLPattern::SchemeMasks GetSupportedSchemeType(const GURL& url) {
@@ -255,10 +303,19 @@ void PageLoadHistograms::Dump(WebFrame* frame) {
       PLT_HISTOGRAM("PLT.BeginToFinish_LinkLoadCacheOnly",
                     begin_to_finish_all_loads);
       break;
+    case NavigationState::PRERENDER_LOAD:
+      PLT_HISTOGRAM("PLT.BeginToFinishDoc_PrerenderLoad",
+                    begin_to_finish_doc);
+      PLT_HISTOGRAM("PLT.BeginToFinish_PrerenderLoad",
+                    begin_to_finish_all_loads);
+      break;
     default:
       break;
   }
 
+  UpdatePrerenderHistograms(navigation_state, begin, finish_all_loads,
+                            begin_to_finish_all_loads);
+
   // Histograms to determine if DNS prefetching has an impact on PLT.
   static bool use_dns_histogram(base::FieldTrialList::Find("DnsImpact") &&
       !base::FieldTrialList::Find("DnsImpact")->group_name().empty());