Add histograms for ExternalDataUseObserver

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 956e217746ac596da0b6e1729336686571985104..ea5cf9e1861c7642733fb2e2a1f8bf5cf9b3b43e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6453,6 +6453,61 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="DataUsage.ReportSubmission.Failed.Bytes" units="bytes">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Count of bytes in the data use reports that were submitted to the platform
+    external data use observer, and the platform external data use observer
+    notified that the submission failed. Recorded every time platform external

[sclittle, 2015/12/08 02:25:41]

nit: add "the" before "platform external..."

[tbansal1, 2015/12/08 04:04:32]

Done.

+    data use observer notifies that submission of data use report failed. This
+    does not include the reports that timed-out.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.ReportSubmission.Lost.Bytes" units="bytes">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Count of bytes in the data use reports that were lost before an attempt is
+    made to submit it to the C++ external data use observer. Recorded every time
+    a report is lost before an attempt is made to submit it to the external data
+    use observer. A submission may be lost if the data use report  could not be

[sclittle, 2015/12/08 02:25:41]

nit: fix double space between words

[tbansal1, 2015/12/08 04:04:32]

Done.

+    buffered due to internal buffers being full.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.ReportSubmission.Successful.Bytes" units="bytes">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Count of bytes in the data use reports that were submitted to the platform
+    external data use observer and the platform external data use observer
+    notified that the submission was successful.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.ReportSubmission.TimedOut.Bytes" units="bytes">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Count of bytes in the data use reports whose submission to the platform
+    external data use observer timed out. Recorded every time submission of a
+    report to the platform external data use observer times out.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.ReportSubmissionResult"
+    enum="DataUsageReportSubmissionResult">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Result of data usage report submission. Recorded every time a report is
+    either submitted to the platform external data use observer, and when an

[sclittle, 2015/12/08 02:25:41]

nit: this "Recorded every time..." sentence is still unclear - isn't success
only recorded after the platform EDUObserver notifies that success happened, not
when the report is initially submitted to it?

I'd just remove this sentence altogether - it doesn't seem to me that it adds
any information.

[tbansal1, 2015/12/08 04:04:32]

Done.

+    attempt could not be made to submit the report.
+  </summary>
+</histogram>
+
 <histogram name="DataUse.MessageSize" units="bytes">
   <owner>amohammadkhan@chromium.org</owner>
   <owner>bengr@chromium.org</owner>
@@ -58334,6 +58389,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="10" label="Diabled directly from the First Run Experience"/>
 </enum>
 
+<enum name="DataUsageReportSubmissionResult" type="int">
+  <int value="0" label="Successful"/>
+  <int value="1" label="Failed"/>
+  <int value="2" label="Timed out"/>
+  <int value="3" label="Lost"/>

[sclittle, 2015/12/08 02:25:41]

FYI: If the buffer ever gets too big, there'll be a huge amount of "Lost" values
recorded here for each tiny DataUse report that gets lost. Is there any value in
recording the "Lost" case together with the other cases here?

[tbansal1, 2015/12/08 04:04:32]

That's possible if there are many matching labels (more than 300?). I think it
is still useful to have the count in a separate dashboard (partly because I am
hoping all errors to have very low count).

+</enum>
+
 <enum name="DataUseServices" type="int">
   <int value="0" label="Not Tagged"/>
   <int value="1" label="Suggestions"/>