[Cast Channel] Add support for nonce challenge to Cast channel authentication.

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 a6f577cfd8c1c6a906a6b6a1187101c11381b326..ef24e9969b8ab4adbd4d0b203689e8a6d49af313 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6265,6 +6265,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Cast.Channel.Nonce" enum="CastNonceStatus">
+  <owner>ryanchung@google.com</owner>
+  <summary>
+    Records whether the correct nonce challenge was in the Cast receiver's
+    response.
+  </summary>
+</histogram>
+
 <histogram name="Cast.Network.Down.Duration.In.Seconds" units="seconds">
   <owner>cast-analytics@google.com</owner>
   <summary>
@@ -83730,6 +83738,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="3" label="CertRevoked"/>
 </enum>
 
+<enum name="CastNonceStatus" type="int">
+  <int value="0" label="Match"/>
+  <int value="1" label="Mismatch"/>
+  <int value="2" label="Missing"/>
+</enum>
+
 <enum name="CastOverlayEvents" type="int">
   <int value="0" label="Created"/>
   <int value="1" label="Shown"/>