NQE: Record correlation metric in UMA

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 0fb3604625d680dfc4a3eb3b0c737a1d200a7a76..00007cdacf2e24a6b4ae051083d776d1782f9e7b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -35709,6 +35709,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NQE.Correlation.ResourceLoadTime.0Kb_128Kb">
+  <owner>tbansal@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    Records estimated network quality (estimated RTT, estimated downlink
+    bandwidth), resource load size, and the resource load time in a single UMA
+    sample. This metric is recorded randomly when a resource load finishes.

[Ilya Sherman, 2016/07/21 23:39:51]

Please document how the metric is constructed, and that this is intended to be
analyzed via custom scripts rather than on the dashboard.

[tbansal1, 2016/07/22 00:15:44]

Done.

+  </summary>
+</histogram>
+
 <histogram name="NQE.DifferenceRTTActualAndEstimated" units="ms">
   <obsolete>
     Replaced in June 2016 by NQE.Accuracy.HttpRTT.* metrics.