Add UMA metrics and finch experiment for DTLS1.2 in WebRTC.

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 c7a6b843898f0197b5982f07a03c6fc62acfc264..f7d14196d9e7d665b1c49feda5daf8157bfec14d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -50390,6 +50390,23 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebRTC.PeerConnection.SrtpCryptoSuite"
+    enum="DTLS_SRTPCryptoSuite">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    Counters on the type of SRTP crypto suites used by WebRTC. This is collected
+    whenever the transport signals the OnCompleted event.
+  </summary>
+</histogram>
+
+<histogram name="WebRTC.PeerConnection.SslCipherSuite" enum="SSLCipherSuite">
+  <owner>guoweis@chromium.org</owner>
+  <summary>
+    Counters on the type of SSL cipher suites used by WebRTC. This is collected
+    whenever the transport signals the OnCompleted event.
+  </summary>
+</histogram>
+
 <histogram name="WebRTC.PeerConnection.TimeToConnect" units="milliseconds">
   <owner>mallinath@chromium.org</owner>
   <summary>Time to setup a peer to peer call with PeerConnection.</summary>
@@ -55046,6 +55063,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Batch"/>
 </enum>
 
+<enum name="DTLS_SRTPCryptoSuite" type="int">
+  <summary>
+    DTLS/SRTP crypto suites from the IANA registry as specified at
+    https://tools.ietf.org/html/rfc5764#section-4.1.2
+  </summary>
+  <int value="1" label="SRTP_AES128_CM_SHA1_80"/>
+  <int value="2" label="SRTP_AES128_CM_SHA1_32"/>
+  <int value="5" label="SRTP_NULL_SHA1_80"/>
+  <int value="6" label="SRTP_NULL_SHA1_32"/>
+</enum>
+
 <enum name="DumpOutcome" type="int">
   <int value="0" label="Success"/>
   <int value="1" label="Failure"/>
@@ -78625,6 +78653,14 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="WebFont.DecodeSpeed"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="WebRTCMediaType" separator=".">
+  <suffix name="Audio" label="Audio"/>
+  <suffix name="Video" label="Video"/>
+  <suffix name="Data" label="Data"/>
+  <affected-histogram name="WebRTC.PeerConnection.SrtpCryptoSuite"/>
+  <affected-histogram name="WebRTC.PeerConnection.SslCipherSuite"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="WebStoreLinkExperiment">
   <suffix name="Disabled" label="Neither extra webstore link is visible"/>
   <suffix name="FooterLink" label="Link in bottom right of footer"/>