[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 579764af88e3d65748a972badeec900e0ee1eb52..5ccf93e92c78ff209211db38bd2784a66bb9b3bb 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5605,6 +5605,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Cast.Channel.Nonce" enum="CastNonce">
+  <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>
@@ -79248,6 +79256,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="3" label="CertRevoked"/>
 </enum>
 
+<enum name="CastNonce" 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"/>