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 c11089e05d692f90906ee3048e51e2229d74b7b9..66a745203e53e08c6608903ccb26ebb34f96e62c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -41668,6 +41668,37 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.ContentSuggestions.TimeUntilFirstSoftTrigger"

[Ilya Sherman, 2017/04/12 22:53:42]

nit: Please add base="true" to this histogram name, as it seems you never emit
to it directly (as opposed to the suffixed versions)

[jkrcal, 2017/04/13 08:42:59]

Oh, cool! I did not know this parameter. Done.

+    units="ms">
+  <owner>jkrcal@chromium.org</owner>
+  <summary>
+    Android: The time difference between the last fetch and the first fetch
+    trigger. The first trigger may come before the respective scheduling
+    interval elapses, or after this moment. This metric is recorded once per

[Ilya Sherman, 2017/04/12 22:53:42]

I don't quite understand this description.  One concern based on my unclear
understanding: Is it possible for the values recorded to this histogram to be
negative, or are they guaranteed to be non-negative?  UMA histograms
unfortunately do not support negative values.

[jkrcal, 2017/04/13 08:42:59]

Yes, this is guaranteed to be non-negative. I've also rephrased the description.

+    each soft fetch (per lifetime of a Chrome instance). This is used to
+    understand how changing scheduling intervals will impact traffic of
+    background fetches.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.ContentSuggestions.TimeUntilPersistentFetch"
+    units="ms">
+  <owner>jkrcal@chromium.org</owner>
+  <summary>
+    Android: The time since the last fetch recorded upon a persistent fetch.
+    This is used to understand what are the real persistent fetching intervals
+    in the wild.
+  </summary>
+</histogram>
+
+<histogram name="NewTabPage.ContentSuggestions.TimeUntilSoftFetch" units="ms">
+  <owner>jkrcal@chromium.org</owner>
+  <summary>
+    Android: The time since the last fetch recorded upon a soft fetch. This is

[Ilya Sherman, 2017/04/12 22:53:42]

nit: Please add a comma before "recorded"; ditto above.

[jkrcal, 2017/04/13 08:42:59]

Done.

+    used to understand what are the real soft fetching intervals in the wild.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.ContentSuggestions.UIUpdateResult"
     enum="ContentSuggestionsUIUpdateResult">
   <obsolete>
@@ -125340,6 +125371,17 @@ from previous Chrome versions.
   <affected-histogram name="Setup.Install.LzmaUnPackStatus"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="UserClasses">
+  <suffix name="RareNTPUser" label="Rare NTP user"/>
+  <suffix name="ActiveNTPUser" label="Active NTP user"/>
+  <suffix name="ActiveSuggestionsConsumer" label="Active suggestions consumer"/>
+  <affected-histogram
+      name="NewTabPage.ContentSuggestions.TimeUntilFirstSoftTrigger"/>
+  <affected-histogram
+      name="NewTabPage.ContentSuggestions.TimeUntilPersistentFetch"/>
+  <affected-histogram name="NewTabPage.ContentSuggestions.TimeUntilSoftFetch"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="UserScriptRunLocation" separator=".">
   <suffix name="DocumentStart" label="Scripts with run_at: document_start."/>
   <suffix name="DocumentEnd" label="Scripts with run_at: document_end."/>