Implement exponential backoff for failed Me2Me authentication attempts

remoting/protocol/jingle_messages.h

Index: remoting/protocol/jingle_messages.h
diff --git a/remoting/protocol/jingle_messages.h b/remoting/protocol/jingle_messages.h
index 3dcdd41ac21588194e35eb0206d0d2ca0424ef02..f404912e3b5b940863b974792b16db59c3184c33 100644
--- a/remoting/protocol/jingle_messages.h
+++ b/remoting/protocol/jingle_messages.h
@@ -35,11 +35,10 @@ struct JingleMessage {
   };
 
   enum Reason {
-    // Currently only termination reasons that can be sent by the host
-    // are understood. All others are converted to UNKNOWN_REASON.
     UNKNOWN_REASON,
     SUCCESS,
     DECLINE,
+    CANCEL,
     GENERAL_ERROR,
     INCOMPATIBLE_PARAMETERS,
   };