Add interface versioning. Methods queryVersion and requireVersion.

mojo/public/js/validator.js

Index: mojo/public/js/validator.js
diff --git a/mojo/public/js/validator.js b/mojo/public/js/validator.js
index 9f2b7cf4db141f3eab218b4e79ce89e69e9c4fa2..e286b8c11337c6dadd31618320c33e7d5e18f621 100644
--- a/mojo/public/js/validator.js
+++ b/mojo/public/js/validator.js
@@ -210,6 +210,14 @@ define("mojo/public/js/validator", [
     return validationError.NONE;
   };
 
+  Validator.prototype.validateMessageIsResponse = function
+    validateMessageIsResponse(message) {
+    if (message.expectsResponse() || !message.isResponse()){
+      return validationError.MESSAGE_HEADER_INVALID_FLAGS;
+    }
+    return validationError.NONE;
+  }
+
   // Returns the message.buffer relative offset this pointer "points to",
   // NULL_MOJO_POINTER if the pointer represents a null, or JS null if the
   // pointer's value is not valid.