Expose packet loss counts from QUIC to NetworkQualityEstimator

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 5f2f65bc9f4c309b10c54c899bc26158933387c5..2667a4db820b76e5cea1c757759213da39a987bc 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -31353,6 +31353,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NQE.PacketLossRate" units="100 times">
+  <owner>bengr@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
+  <summary>
+    Rough estimate of the packet loss rate multiplied by 100, before a

[bengr, 2016/02/19 00:45:09]

Why is it rough?

[tbansal1, 2016/02/26 01:15:00]

Done.

+    connectivity change is detected.
+
+    This metric is recorded when a connectivity change is detected. This will

[bengr, 2016/02/19 00:45:09]

Is this per network session? I.e., my desktop Chrome will only report once, but
my Android Chrome will report several times a day? 

I think we should find a better interval. How about on every page load? Or on
every connectivity change (including startup) and at least once every k hours?

[tbansal1, 2016/02/26 01:15:00]

Changed it to record on every page load.

+    miss data from users whose connection type never changes and will be biased
+    to users whose connection type changes frequently.
+  </summary>
+</histogram>
+
 <histogram name="NQE.PeakKbps" units="Kbps">
   <owner>bengr@chromium.org</owner>
   <owner>tbansal@chromium.org</owner>
@@ -86051,6 +86064,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="NQE.DifferenceRTTActualAndEstimated"/>
   <affected-histogram name="NQE.DifferenceRTTEstimatedAndActual"/>
   <affected-histogram name="NQE.FastestRTT"/>
+  <affected-histogram name="NQE.PacketLossRate"/>
   <affected-histogram name="NQE.PeakKbps"/>
   <affected-histogram name="NQE.RatioEstimatedToActualRTT"/>
   <affected-histogram name="NQE.RTT.Percentile0"/>