Connecting UserClassifier to NtpSnippetsFetcher

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 51b2c69057a9778abc76969b5c093972495af944..6a3e355a624d33e067294a6b07ca5655c1874c10 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -108122,7 +108122,18 @@ value.
 
 <histogram_suffixes name="RequestThrottlerTypes">
   <suffix name="SuggestionFetcher"
-      label="Fetcher for content suggestions on mobile NTP"/>
+      label="Fetcher for content suggestions on mobile NTP">
+    <obsolete>
+      Deprecated in 10/2016.
+    </obsolete>
+  </suffix>
+  <suffix name="SuggestionFetcherRareNTPUser"
+      label="Fetcher for content suggestions on mobile NTP - rare NTP users"/>
+  <suffix name="SuggestionFetcherActiveNTPUser"
+      label="Fetcher for content suggestions on mobile NTP - active NTP users"/>
+  <suffix name="SuggestionFetcherActiveSuggestionsConsumer"
+      label="Fetcher for content suggestions on mobile NTP - active
+             suggestions consumers"/>

[jwd, 2016/10/07 14:28:24]

Do these three overlap? It seems like an active NTP user could also be an active
suggestions consumer. Is there any way to get a total view of these three cases?

And fyi, suffixes can apply to histogram names generated by suffixes. So you
could also do this with a new suffix applying to the ...SuggestionFetcher
histograms. I don't think you'd be able to obsolete the base
...SuggestionFetcher histograms like you're doing here though.

[jkrcal, 2016/10/07 14:36:51]

No, these do not overlap. You need to look at the three classes of histograms to
get an overview.
I actually don't want to add more structure to it because I want to keep the
class RequestThrottler as simple as possible
 (and it is and will be used for other cases than for these three classes of
users, see SuggestionThumbnailFetcher below).
Huh, interesting :) Not desired in this case: I want a 1 to 1 correspondence
between these suffixes and entries in kRequestTypeInfo in request_throttler.c

   <suffix name="SuggestionThumbnailFetcher"
       label="Fetcher for article thumbnails on mobile NTP"/>
   <affected-histogram name="NewTabPage.RequestThrottler.PerDay"/>