Update the protocol buffer compiler plugin to use Int64 from the fixnum package

test/test_util.dart

Index: test/test_util.dart
diff --git a/test/test_util.dart b/test/test_util.dart
index a708e613aac707828007b214b190738745e9c8cc..6f6c391da36b530293eca3be37707c63f8bd84d4 100644
--- a/test/test_util.dart
+++ b/test/test_util.dart
@@ -6,6 +6,7 @@ library test_util;
 
 import 'dart:typed_data';
 
+import 'package:fixnum/fixnum.dart';
 import 'package:protobuf/protobuf.dart';
 import 'package:unittest/unittest.dart';
 
@@ -13,20 +14,14 @@ import '../out/protos/google/protobuf/unittest_import.pb.dart';
 import '../out/protos/google/protobuf/unittest.pb.dart';
 
 
-make64(lo, [hi = null]) {
+Int64 make64(lo, [hi = null]) {
   if (hi == null) hi = lo < 0 ? -1 : 0;
-  return new ByteData(8)
-      ..setUint32(0, lo, Endianness.LITTLE_ENDIAN)
-      ..setUint32(4, hi, Endianness.LITTLE_ENDIAN);
+  return new Int64.fromInts(hi, lo);
 }
 
 expect64(lo, [hi = null]) {
-  final expected = make64(lo, hi);
-  return predicate((actual) {
-    get(data, offset) => data.getUint32(offset, Endianness.LITTLE_ENDIAN);
-    return get(actual, 0) == get(expected, 0) &&
-        get(actual, 4) == get(expected, 4);
-  });
+  final Int64 expected = make64(lo, hi);
+  return predicate((Int64 actual) => actual == expected);
 }
 
 void assertAllExtensionsSet(TestAllExtensions message) {