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

lib/unknown_field_set.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 UnknownFieldSet {
 
   final Map<int, UnknownFieldSetField> _fields =
       new Map<int, UnknownFieldSetField>();
@@ skipping 74 matching lines @@
   _checkFieldNumber(int number) {
     if (number == 0) {
       throw new ArgumentError('Zero is not a valid field number.');
     }
   }
 
   void mergeFixed32Field(int number, int value) {
     _getField(number).addFixed32(value);
   }
 
-  void mergeFixed64Field(int number, ByteData value) {
+  void mergeFixed64Field(int number, Int64 value) {
     _getField(number).addFixed64(value);
   }
 
   void mergeGroupField(int number, UnknownFieldSet value) {
     _getField(number).addGroup(value);
   }
 
   void mergeLengthDelimitedField(int number, List<int> value) {
     _getField(number).addLengthDelimited(value);
   }
 
-  void mergeVarintField(int number, ByteData value) {
+  void mergeVarintField(int number, Int64 value) {
     _getField(number).addVarint(value);
   }
 
   UnknownFieldSetField _getField(int number) {
     _checkFieldNumber(number);
     return _fields.putIfAbsent(number, () => new UnknownFieldSetField());
   }
 
   bool operator ==(other) {
     if (other is! UnknownFieldSet) return false;
@@ skipping 33 matching lines @@
   void writeToCodedBufferWriter(CodedBufferWriter output) {
     for (int key in _fields.keys) {
       _fields[key].writeTo(key, output);
     }
   }
 }
 
 class UnknownFieldSetField {
 
   final List<List<int>> lengthDelimited = <List<int>>[];
-  final List<ByteData> varints = <ByteData>[];
+  final List<Int64> varints = <Int64>[];
   final List<int> fixed32s = <int>[];
-  final List<ByteData> fixed64s = <ByteData>[];
+  final List<Int64> fixed64s = <Int64>[];
   final List<UnknownFieldSet> groups = <UnknownFieldSet>[];
 
   bool operator ==(other) {
     if (other is! UnknownFieldSetField) return false;
 
     UnknownFieldSetField o = other;
     if (lengthDelimited.length != o.lengthDelimited.length) return false;
     for (int i = 0; i < lengthDelimited.length; i++) {
       if (!_areListsEqual(o.lengthDelimited[i], lengthDelimited[i])) {
         return false;
@@ skipping 33 matching lines @@
   }
 
   void addLengthDelimited(List<int> value) {
     lengthDelimited.add(value);
   }
 
   void addFixed32(int value) {
     fixed32s.add(value);
   }
 
-  void addFixed64(ByteData value) {
+  void addFixed64(Int64 value) {
     fixed64s.add(value);
   }
 
-  void addVarint(ByteData value) {
+  void addVarint(Int64 value) {
     varints.add(value);
   }
 
   bool hasRequiredFields() => false;
 
   bool isInitialized() => true;
 
   int get length => values.length;
 }