[NoStatePrefetch] Add performance histograms.

chrome/browser/prerender/prerender_histograms.cc

Index: chrome/browser/prerender/prerender_histograms.cc
diff --git a/chrome/browser/prerender/prerender_histograms.cc b/chrome/browser/prerender/prerender_histograms.cc
index 28c43c0968095a78f4c072d41a676220737994bf..4e97663049a8d3e75b14b55e98a28ec60af7f2cc 100644
--- a/chrome/browser/prerender/prerender_histograms.cc
+++ b/chrome/browser/prerender/prerender_histograms.cc
@@ -13,6 +13,7 @@
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_util.h"
+#include "net/http/http_cache.h"
 
 namespace prerender {
 
@@ -37,7 +38,7 @@ int GetResourceType(bool is_main_resource, bool is_redirect, bool is_no_store) {
 // Similar to UMA_HISTOGRAM_ENUMERATION but allows a dynamic histogram name.
 // Records a sample such as 0 <= sample < bucket_count, in a histogram with
 // |bucket_count| buckets of width 1 each.
-void RecordHistogramEnum(std::string histogram_name,
+void RecordHistogramEnum(const std::string& histogram_name,
                          base::HistogramBase::Sample sample,
                          base::HistogramBase::Sample bucket_count) {
   DCHECK_LT(sample, bucket_count);
@@ -47,6 +48,18 @@ void RecordHistogramEnum(std::string histogram_name,
   histogram_pointer->Add(sample);
 }
 
+// Similar to UMA_HISTOGRAM_CUSTOM_TIMES but allows a dynamic histogram name.
+void RecordHistogramTime(const std::string& histogram_name,
+                         base::TimeDelta time_min,
+                         base::TimeDelta time_max,
+                         base::TimeDelta sample,
+                         base::HistogramBase::Sample bucket_count) {
+  base::HistogramBase* histogram_pointer = base::Histogram::FactoryTimeGet(
+      histogram_name, time_min, time_max, bucket_count,
+      base::HistogramBase::kUmaTargetedHistogramFlag);
+  histogram_pointer->AddTime(sample);
+}
+
 // Time window for which we will record windowed PLTs from the last observed
 // link rel=prefetch tag. This is not intended to be the same as the prerender
 // ttl, it's just intended to be a window during which a prerender has likely
@@ -439,10 +452,51 @@ void PrerenderHistograms::RecordPrefetchRedirectCount(
   RecordHistogramEnum(histogram_name, redirect_count, kMaxRedirectCount);
 }
 
+void PrerenderHistograms::RecordFirstContentfulPaint(
+    Origin origin,
+    bool is_no_store,
+    base::TimeDelta time,
+    base::TimeDelta prefetch_age) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (!prefetch_age.is_zero()) {
+    DCHECK_NE(origin, ORIGIN_NONE);
+    RecordHistogramTime(GetHistogramName(origin, IsOriginWash(),
+                                         "Prerender.NoStatePrefetchAge"),
+                        base::TimeDelta::FromMilliseconds(10),
+                        base::TimeDelta::FromMinutes(30), prefetch_age, 50);
+  }
+
+  RecordHistogramTime(GetFirstContentfulPaintHistogramName(
+                          origin, IsOriginWash(), is_no_store, prefetch_age),
+                      base::TimeDelta::FromMilliseconds(10),
+                      base::TimeDelta::FromMinutes(2), time, 50);
+}
+
 bool PrerenderHistograms::IsOriginWash() const {
   if (!WithinWindow())
     return false;
   return origin_wash_;
 }
 
+// static
+std::string PrerenderHistograms::GetFirstContentfulPaintHistogramName(
+    Origin origin,
+    bool is_wash,
+    bool is_no_store,
+    base::TimeDelta prefetch_age) {
+  std::string histogram_base_name;
+  if (prefetch_age.is_zero()) {
+    histogram_base_name = "NoStatePrefetchTTFCP.Reference";
+  } else {
+    histogram_base_name = prefetch_age < base::TimeDelta::FromMinutes(
+                                             net::HttpCache::kPrefetchReuseMins)
+                              ? "NoStatePrefetchTTFCP.Warm"
+                              : "NoStatePrefetchTTFCP.Cold";
+  }
+
+  histogram_base_name += is_no_store ? ".NoStore" : ".Cacheable";
+  return GetHistogramName(origin, is_wash, histogram_base_name);
+}
+
 }  // namespace prerender