Fix issues with protobuf equality comparisons

lib/src/protobuf/utils.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of protobuf;
 
 // TODO(antonm): reconsider later if PbList should take care of equality.
 bool _deepEquals(lhs, rhs) {
+  // Some GeneratedMessages implement Map, so test this first.
+  if (lhs is GeneratedMessage) return lhs == rhs;
+  if (rhs is GeneratedMessage) return false;
   if ((lhs is List) && (rhs is List)) return _areListsEqual(lhs, rhs);
   if ((lhs is Map) && (rhs is Map)) return _areMapsEqual(lhs, rhs);
   if ((lhs is ByteData) && (rhs is ByteData)) {
     return _areByteDataEqual(lhs, rhs);
   }
   return lhs == rhs;
 }
 
 bool _areListsEqual(List lhs, List rhs) {
   range(i) => new Iterable.generate(i, (i) => i);
 
   if (lhs.length != rhs.length) return false;
   return range(lhs.length).every((i) => _deepEquals(lhs[i], rhs[i]));
 }
 
 bool _areMapsEqual(Map lhs, Map rhs) {
   if (lhs.length != rhs.length) return false;
   return lhs.keys.every((key) => _deepEquals(lhs[key], rhs[key]));
 }
 
 bool _areByteDataEqual(ByteData lhs, ByteData rhs) {
   asBytes(d) => new Uint8List.view(d.buffer, d.offsetInBytes, d.lengthInBytes);
   return _areListsEqual(asBytes(lhs), asBytes(rhs));
 }
 
 List/*<T>*/ sorted/*<T>*/(Iterable/*<T>*/ list) => new List.from(list)..sort();