Update the protocol buffer library to use Int64 from the fixnum package

lib/pb_list.dart

 // Copyright (c) 2011, 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;
 
 class PbList<E> extends Object with ListMixin<E> implements List<E> {
 
   PbList() : _wrappedList = <E>[];
 
@@ skipping 149 matching lines @@
       throw new ArgumentError('Illegal to add value (${val}):'
           ' out of range for uint32');
     }
   }
 }
 
 /**
  * A [PbList] that requires its elements to be [int]s in the range
  * [:2^-63, 2^63 - 1:].
  */
-class PbSint64List extends PbList<ByteData> {
-  void _validateElement(ByteData val) {
+class PbSint64List extends PbList<Int64> {
+  void _validateElement(Int64 val) {
     if (!_isSigned64(val)) {
       throw new ArgumentError('Illegal to add value (${val}):'
           ' out of range for sint64');
     }
   }
 }
 
 /**
  * A [PbList] that requires its elements to be [int]s in the range
  * [:0, 2^64 - 1:].
  */
-class PbUint64List extends PbList<ByteData> {
-  void _validateElement(ByteData val) {
+class PbUint64List extends PbList<Int64> {
+  void _validateElement(Int64 val) {
     if (!_isUnsigned64(val)) {
       throw new ArgumentError('Illegal to add value (${val}):'
           ' out of range for uint64');
     }
   }
 }
 
 /**
  * A [PbList] that requires its elements to be [double]s in the range
  * [:-3.4E38, 3.4E38:], i.e., with the IEEE single-precision range.
  */
 class PbFloatList extends PbList<double> {
   void _validateElement(double val) {
     if (!_isFloat32(val)) {
       throw new ArgumentError('Illegal to add value (${val}):'
           ' out of range for float');
     }
   }
 }