[Mojo] Make javascript enums extensible.

mojo/public/js/codec.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 define("mojo/public/js/codec", [
   "mojo/public/js/unicode",
   "mojo/public/js/buffer",
 ], function(unicode, buffer) {
 
   var kErrorUnsigned = "Passing negative value to unsigned";
@@ skipping 693 matching lines @@
   Double.encodedSize = 8;
 
   Double.decode = function(decoder) {
     return decoder.readDouble();
   };
 
   Double.encode = function(encoder, val) {
     encoder.writeDouble(val);
   };
 
+  function Enum(cls) {
+    this.cls = cls;
+  }
+
+  Enum.prototype.encodedSize = 4;
+
+  Enum.prototype.decode = function(decoder) {
+    return decoder.readInt32();
+  };
+
+  Enum.prototype.encode = function(encoder, val) {
+    encoder.writeInt32(val);
+  };
+
   function PointerTo(cls) {
     this.cls = cls;
   }
 
   PointerTo.prototype.encodedSize = 8;
 
   PointerTo.prototype.decode = function(decoder) {
     var pointer = decoder.decodePointer();
     if (!pointer) {
       return null;
@@ skipping 132 matching lines @@
   exports.Uint8 = Uint8;
   exports.Int16 = Int16;
   exports.Uint16 = Uint16;
   exports.Int32 = Int32;
   exports.Uint32 = Uint32;
   exports.Int64 = Int64;
   exports.Uint64 = Uint64;
   exports.Float = Float;
   exports.Double = Double;
   exports.String = String;
+  exports.Enum = Enum;
   exports.NullableString = NullableString;
   exports.PointerTo = PointerTo;
   exports.NullablePointerTo = NullablePointerTo;
   exports.ArrayOf = ArrayOf;
   exports.NullableArrayOf = NullableArrayOf;
   exports.PackedBool = PackedBool;
   exports.Handle = Handle;
   exports.NullableHandle = NullableHandle;
   exports.Interface = Interface;
   exports.NullableInterface = NullableInterface;
   exports.MapOf = MapOf;
   exports.NullableMapOf = NullableMapOf;
   return exports;
 });