Add a histogram for omnibox answer suggestion types.

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 60530d1d4d3e5fafa88a9623db742098c9a71c52..7d994b382edd2b86f8892119e2d6a59f16ef430d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -43189,6 +43189,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Omnibox.AnswerType" enum="SuggestionAnswerType">

[Mark P, 2017/03/02 20:59:35]

Please consider a new name, perhaps one with "Parse" in the name.  (Better
aligns with Omnibox.AnswerParseSuccess histogram, and also doesn't mislead. 
From the name, I would guess this has to do with answers that are displayed.)

[Justin Donnelly, 2017/03/02 21:21:25]

Done.

+  <owner>jdonnelly@chromium.org</owner>
+  <summary>
+    The number of times each answer type (e.g. weather, sports score) was

[Mark P, 2017/03/02 20:59:35]

nit: comma after "e.g."

[Justin Donnelly, 2017/03/02 21:21:25]

Done.

+    received and parsed successfully.

[Mark P, 2017/03/02 20:59:35]

The way this histogram reads now, it's only useful to compare counts against
each other.  Is there any other way you'd like to compare them, e.g., against
the total number of responses received and parsed successfully?  That is,
normalized.  If not, then nothing to do here.  If so, then either
(a) if there is a histogram that already records this information (I don't think
so, but I'm not sure), add to this histogram description a reference to the
normalizing histogram
or
(b) consider adding the histogram for normalization

[Justin Donnelly, 2017/03/02 21:21:25]

Done (a). Can you double-check that what I wrote makes sense and addresses your
comment? I'm a little confused because you mentioned AnswerParseSuccess in an
earlier comment but then stated here that you don't think a histogram that
records the number of responses parsed successfully. I'm worried I'm missing
something. :)

+  </summary>
+</histogram>
+
 <histogram name="Omnibox.CharTypedToRepaintLatency" units="ms">
   <owner>asvitkine@chromium.org</owner>
   <owner>mpearson@chromium.org</owner>
@@ -109780,6 +109788,19 @@ from previous Chrome versions.
   <int value="2" label="Load failed"/>
 </enum>
 
+<enum name="SuggestionAnswerType" type="int">
+  <summary>Type of Answer shown in omnibox suggestion list.</summary>

[Mark P, 2017/03/02 23:41:04]

Where is the suggest server code for this?  Can you make sure it has the
standard warning label about not being able to change the values?
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histo...

[Justin Donnelly, 2017/03/03 00:39:32]

This is AnswerTriggererKey in
http://google3/logs/proto/suggest/suggest_extensions.proto. I'll add the
warning.

+  <int value="1" label="Dictionary"/>
+  <int value="2" label="Finance"/>
+  <int value="3" label="Knowledge graph"/>
+  <int value="5" label="Sports"/>
+  <int value="6" label="Sunrise"/>
+  <int value="7" label="Translation"/>
+  <int value="8" label="Weather"/>
+  <int value="9" label="When is"/>
+  <int value="10" label="Currency"/>
+</enum>
+
 <enum name="SuggestionsResponseState" type="int">
   <int value="0" label="Empty response received from the server."/>
   <int value="1" label="Invalid response received from the server."/>