Add histograms for data usage

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 49aa452bbb54c688253b4ddd0676e913634e60bf..55c8114833705903ece70d0449eb1eb3ebddf227 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6566,6 +6566,50 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="DataUsage.MatchingRulesCount.Invalid" units="count">
+  <owner>bengr@chromium.org</owner>
+  <owner>rajendrant@chromium.org</owner>
+  <summary>
+    The number of invalid matching rules fetched from the platform external data

[tbansal1, 2016/01/14 06:59:55]

Please comment on when this UMA is recorded. Something like: "A sample is
recorded everytime..."

Same for other UMA.

[Raj, 2016/01/15 06:23:24]

Done.

+    use observer.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.MatchingRulesCount.Valid" units="count">
+  <owner>bengr@chromium.org</owner>
+  <owner>rajendrant@chromium.org</owner>
+  <summary>
+    The number of valid matching rules fetched from the platform external data
+    use observer.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.Perf.MatchingRuleFirstFetchDuration" units="ms">

[tbansal1, 2016/01/14 06:59:55]

Say milliseconds to avoid ambiguity with microseconds. Here, and below.

[Raj, 2016/01/15 06:23:24]

Done.

+  <owner>bengr@chromium.org</owner>
+  <owner>rajendrant@chromium.org</owner>
+  <summary>
+    The time taken to fetch the matching rules for the first time from the
+    platform external data use observer. This will be the duration from the time

[tbansal1, 2016/01/14 06:59:55]

s/will be the/is/ OR
measures?

Similarly for other UMA in this file.

[Raj, 2016/01/15 06:23:24]

Done.

+    fetch was called to the time the rules are returned asynchronously.
+  </summary>
+</histogram>
+
+<histogram name="DataUsage.Perf.ReportSubmissionDuration" units="ms">
+  <owner>bengr@chromium.org</owner>
+  <owner>rajendrant@chromium.org</owner>
+  <summary>
+    The time taken to submit the data use reports to the platform external data
+    use observer. This will be the duration from the time reports are submitted
+    to the time report submitted asynchronous callback was received.

[tbansal1, 2016/01/14 06:59:55]

Is this recorded only when callback indicates success or it the callback result
does not matter?

[Raj, 2016/01/15 06:23:24]

Callback result does not matter.

+  </summary>
+</histogram>
+
+<histogram name="DataUsage.Perf.URLRegexMatchDuration" units="ms">
+  <owner>bengr@chromium.org</owner>
+  <owner>rajendrant@chromium.org</owner>
+  <summary>The time taken for a regular expression to process an URL</summary>
+</histogram>
+
 <histogram name="DataUsage.ReportSubmission.Bytes" units="bytes">
   <owner>bengr@chromium.org</owner>
   <owner>tbansal@chromium.org</owner>