[Prerender] first contentful paint histograms.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 7eb08c64ad2ae4560e7d25c20e26d46dc304714e..a19f855a3f2acd574a9d2c8dcab39315d29897ba 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -49628,6 +49628,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Prerender.PerceivedTTFCPRecorded" enum="BooleanRecorded">
+  <owner>droger@chromium.org</owner>
+  <owner>mattcary@chromium.org</owner>
+  <owner>pasko@chromium.org</owner>
+  <summary>
+    Whether perceived TTFCP was recorded successfully. If true, there is an
+    associated PrefetchTTFCP that records the TTFCP from the swapped-in
+    navigation start. If false, no PrefetchTTFCP was recorded.
+  </summary>
+</histogram>
+
 <histogram name="Prerender.PercentLoadDoneAtSwapin">
   <owner>pasko@chromium.org</owner>
   <summary>
@@ -49653,6 +49664,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Prerender.PrefetchTTFCP" units="ms">
+  <owner>droger@chromium.org</owner>
+  <owner>mattcary@chromium.org</owner>
+  <owner>pasko@chromium.org</owner>
+  <summary>
+    Time to first contentful paint (TTFCP) for navigations related to prefetch
+    (including prerender, no-state prefetch, and associated experiments). This
+    measures user-visible TTFCP. For no-state prefetch this is standard
+    navigation-to-FCP; for prerender this is the time from navigation start when
+    the prerender is swapped in to FCP.
+  </summary>
+</histogram>
+
 <histogram name="Prerender.PrerenderCountOf3Max">
   <owner>pasko@chromium.org</owner>
   <summary>
@@ -78091,6 +78115,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Received"/>
 </enum>
 
+<enum name="BooleanRecorded" type="int">
+  <int value="0" label="Not Recorded"/>
+  <int value="1" label="Recorded"/>
+</enum>
+
 <enum name="BooleanRegistered" type="int">
   <int value="0" label="Not Registered"/>
   <int value="1" label="Registered"/>
@@ -113947,6 +113976,7 @@ value.
              prefetched pages (bias)."/>
   <suffix name="Warm" label="Prefetch skips revalidation."/>
   <affected-histogram name="Prerender.NoStatePrefetchTTFCP"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="PrerenderPrefetchMainResourceType" separator=".">
@@ -113955,6 +113985,21 @@ value.
   <affected-histogram name="Prerender.NoStatePrefetchTTFCP.Cold"/>
   <affected-histogram name="Prerender.NoStatePrefetchTTFCP.Reference"/>
   <affected-histogram name="Prerender.NoStatePrefetchTTFCP.Warm"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Reference"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm"/>
+</histogram_suffixes>
+
+<histogram_suffixes name="PrerenderPrefetchPaintVisibility" separator=".">
+  <suffix name="Hidden" label="Page was hidden during rendering."/>
+  <suffix name="Visible" label="Page visible for all of rendering."/>
+  <affected-histogram name="Prerender.PerceivedTTFCPRecorded"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.Cacheable"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.NoStore"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Reference.Cacheable"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Reference.NoStore"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.Cacheable"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.NoStore"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="PrerenderSource" ordering="prefix">
@@ -114008,7 +114053,23 @@ value.
   <affected-histogram name="Prerender.PerceivedPLTMatchedComplete"/>
   <affected-histogram name="Prerender.PerceivedPLTWindowed"/>
   <affected-histogram name="Prerender.PerceivedPLTWindowNotMatched"/>
+  <affected-histogram name="Prerender.PerceivedTTFCPRecorded.Hidden"/>
+  <affected-histogram name="Prerender.PerceivedTTFCPRecorded.Visible"/>
   <affected-histogram name="Prerender.PercentLoadDoneAtSwapin"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.Cacheable.Hidden"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.Cacheable.Visible"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.NoStore.Hidden"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Cold.NoStore.Visible"/>
+  <affected-histogram
+      name="Prerender.PrefetchTTFCP.Reference.Cacheable.Hidden"/>
+  <affected-histogram
+      name="Prerender.PrefetchTTFCP.Reference.Cacheable.Visible"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Reference.NoStore.Hidden"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Reference.NoStore.Visible"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.Cacheable.Hidden"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.Cacheable.Visible"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.NoStore.Hidden"/>
+  <affected-histogram name="Prerender.PrefetchTTFCP.Warm.NoStore.Visible"/>
   <affected-histogram name="Prerender.PrerenderNotSwappedInPLT"/>
   <affected-histogram name="Prerender.PrerendersPerSessionCount"/>
   <affected-histogram name="Prerender.SimulatedLocalBrowsingBaselinePLT"/>