Fix warnings in library-tests.

tests/lib/convert/chunked_conversion_json_decode1_test.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.
 
 import "package:expect/expect.dart";
 import 'dart:convert';
 
 final TESTS = [
     [ 5, '5' ],
     [ -42, '-42' ],
@@ skipping 100 matching lines @@
   return result;
 }
 
 Object decode6(String str) {
   Object result;
   var decoder = new JsonDecoder(null);
   ChunkedConversionSink objectSink =
       new ChunkedConversionSink.withCallback((x) => result = x.single);
   var stringConversionSink = decoder.startChunkedConversion(objectSink);
   ByteConversionSink inputByteSink = stringConversionSink.asUtf8Sink(false);
-  Object tmpBytes = UTF8.encode(str);
+  var tmpBytes = UTF8.encode(str);
   tmpBytes.forEach((b) => inputByteSink.addSlice([0, b, 1], 1, 2, false));
   inputByteSink.close();
   return result;
 }
 
 Object decode7(String str) {
   Object result;
   var decoder = new JsonDecoder(null);
   ChunkedConversionSink objectSink =
       new ChunkedConversionSink.withCallback((x) => result = x.single);
@@ skipping 20 matching lines @@
     var string = test[1];
     Expect.isTrue(isJsonEqual(o, decode(string)));
     Expect.isTrue(isJsonEqual(o, decode2(string)));
     Expect.isTrue(isJsonEqual(o, decode3(string)));
     Expect.isTrue(isJsonEqual(o, decode4(string)));
     Expect.isTrue(isJsonEqual(o, decode5(string)));
     Expect.isTrue(isJsonEqual(o, decode6(string)));
     Expect.isTrue(isJsonEqual(o, decode7(string)));
   }
 }