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 50c656f7c7a6c30490e717e4c25ee2631bfd9119..9831281bafb55601830a4a2145c12b6a4a15179f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -48579,6 +48579,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Prerender.PrefetchTTFCP" units="ms">

[pasko, 2016/12/12 17:32:06]

I think "PrefetchTTFCP for Prerender" is a more confusing concept than
"PerceivedTTFCP for Prerender". Did you consider "PerceivedTTFCP" as a name to
be sending a more confusing message?

[mattcary, 2016/12/12 21:14:55]

PerceivedTTFPC isn't accurate when it's used for NoStatePrefetch. Since the
semantics are very subtle, it seems most straightforward to make it explicit
that these are histograms tuned mostly for the prefetch experiments.

[pasko, 2016/12/15 19:37:51]

So you are saying that it isn't accurate for NoStatePrefetch, but at the same
time it will be used for prefetch experiments? Did you mean "it is not accurate
for non-prefetch uses"? Then how are we supposed to compare it with Prerender? I
am puzzled.

+  <owner>droger@chromium.org</owner>
+  <owner>mattcary@chromium.org</owner>
+  <owner>pasko@chromium.org</owner>
+  <summary>
+    Time to first contentful paint for navigations related to prefetch

[pasko, 2016/12/12 17:32:06]

Please expand this summary more on where the timer starts.

[mattcary, 2016/12/12 21:14:55]

Done.

+    (including prerender, no-state prefetch, and associated experiments).

[pasko, 2016/12/12 17:32:06]

Please expand what a TTFCP of a prefetch is. That's the only place where it is
going to be documented in code, right?

[mattcary, 2016/12/12 21:14:55]

That should be done in the PrerenderPrefetchAge histogram_suffixes I
believe---can you confirm that that documentation propagates up to what's
visible in UMA?

[pasko, 2016/12/15 19:37:51]

The documentation for the suffix would be concatenated with the base
documentation. However, descriptions of those suffixes are pretty slim.

+  </summary>
+</histogram>
+
 <histogram name="Prerender.PrerenderCountOf3Max">
   <owner>pasko@chromium.org</owner>
   <summary>
@@ -111456,6 +111466,7 @@ 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=".">
@@ -111464,6 +111475,20 @@ 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.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">
@@ -111518,6 +111543,20 @@ value.
   <affected-histogram name="Prerender.PerceivedPLTWindowed"/>
   <affected-histogram name="Prerender.PerceivedPLTWindowNotMatched"/>
   <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"/>