Implement UMA and internal data structure for tracking EWOULDBLOCK.

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 8e77773899ccf63bfd8f40942c601467ad2ea673..630dc7d1e745b805ffe6ac0d964f73bfb3e92cba 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -38791,6 +38791,21 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="WebRTC.MaxApplicationConsecutiveEWB">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    The maximum length of consecutive EWOULDBLOCKs generated by WebRTC's socket

[juberti2, 2014/10/23 19:38:46]

Rewrite this to refer to discarded packets instead of EWOULDBLOCK (here and
below)

[guoweis2, 2014/10/24 06:08:55]

Done and changed to bytes.

+    implementation.
+  </summary>
+</histogram>
+
+<histogram name="WebRTC.MaxSystemConsecutiveEWB">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    The maximum length of consecutive EWOULDBLOCKs received from system.
+  </summary>
+</histogram>
+
 <histogram name="WebRTC.NumDataChannelsPerPeerConnection">
   <owner>perkj@chromium.org</owner>
   <summary>
@@ -38802,6 +38817,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="WebRTC.PacketsDroppedByApplicationEWB" units="%">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    The total number of packets dropped by WebRTC's socket layer due to
+    EWOULDBLOCKs.
+  </summary>
+</histogram>
+
 <histogram name="WebRTC.PeerConnection.IPMetrics" enum="PeerConnectionCounters">
   <owner>mallinath@chromium.org</owner>
   <summary>
@@ -55130,6 +55153,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Net.TCP_Connection_Latency_Interval"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="IPProtocolType" separator="_">
+  <suffix name="UDP"/>
+  <suffix name="TCP"/>
+  <affected-histogram name="WebRTC.MaxSystemConsecutiveEWB"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="IPv6_Probe">
   <suffix name="IPv6_probe_skipped"
       label="with IPv6 not probed, and default OS settings used"/>