Create an experiment to study whether too many bindings cause NAT failure

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 038f1e3af28c5691c54601184a12517f32df4e53..d21e89ebf145d37fe0fffeaf7cd91085812c1d2b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -51677,6 +51677,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebRTC.Stun.BatchSuccessPercent" units="percent">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    For clients using a shared source port per STUN binding request toward the
+    specified servers, success rate for requests which received a response with
+    various intervals between requests. Only the first instance of renderers
+    will conduct the trial and log this result. The STUN binding requests are
+    grouped into multiple batches and the success rate is calculated for an
+    individual batch.
+  </summary>
+</histogram>
+
 <histogram name="WebRTC.Stun.ResponseLatency" units="milliseconds">
   <owner>guoweis@chromium.org</owner>
   <summary>
@@ -75782,6 +75794,33 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Platform.Storage.Flash.BadBlocks"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="BatchStunPingParameters" separator=".">
+  <suffix name="5ms.1.5" label="5ms gap, 1 of 5"/>
+  <suffix name="5ms.2.5" label="5ms gap, 2 of 5"/>
+  <suffix name="5ms.3.5" label="5ms gap, 3 of 5"/>
+  <suffix name="5ms.4.5" label="5ms gap, 4 of 5"/>
+  <suffix name="5ms.5.5" label="5ms gap, 5 of 5"/>
+  <suffix name="10ms.1.5" label="10ms gap, 1 of 5"/>
+  <suffix name="10ms.2.5" label="10ms gap, 2 of 5"/>
+  <suffix name="10ms.3.5" label="10ms gap, 3 of 5"/>
+  <suffix name="10ms.4.5" label="10ms gap, 4 of 5"/>
+  <suffix name="10ms.5.5" label="10ms gap, 5 of 5"/>
+  <suffix name="25ms.1.5" label="25ms gap, 1 of 5"/>
+  <suffix name="25ms.2.5" label="25ms gap, 2 of 5"/>
+  <suffix name="25ms.3.5" label="25ms gap, 3 of 5"/>
+  <suffix name="25ms.4.5" label="25ms gap, 4 of 5"/>
+  <suffix name="25ms.5.5" label="25ms gap, 5 of 5"/>
+  <suffix name="50ms.1.5" label="50ms gap, 1 of 5"/>
+  <suffix name="50ms.2.5" label="50ms gap, 2 of 5"/>
+  <suffix name="50ms.3.5" label="50ms gap, 3 of 5"/>
+  <suffix name="50ms.4.5" label="50ms gap, 4 of 5"/>
+  <suffix name="50ms.5.5" label="50ms gap, 5 of 5"/>
+  <affected-histogram name="WebRTC.Stun.BatchSuccessPercent.NoNAT"/>
+  <affected-histogram name="WebRTC.Stun.BatchSuccessPercent.NonSymNAT"/>
+  <affected-histogram name="WebRTC.Stun.BatchSuccessPercent.SymNAT"/>
+  <affected-histogram name="WebRTC.Stun.BatchSuccessPercent.UnknownNAT"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="CacheInstance" separator="." ordering="prefix">
   <suffix name="App"
       label="Collected from the HTML5 Application Cache instance."/>
@@ -77552,6 +77591,7 @@ To add a new entry, add it with any value and run test to compute valid value.
 </histogram_suffixes>
 
 <histogram_suffixes name="NatType" separator=".">
+  <affected-histogram name="WebRTC.Stun.BatchSuccessPercent"/>
   <suffix name="NoNAT"/>
   <suffix name="UnknownNAT"/>
   <suffix name="SymNAT"/>