Use words please.

runtime/observatory/tests/service/weak_properties_test.dart

 // Copyright (c) 2014, 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.
 // VMOptions=--compile-all --error_on_bad_type --error_on_bad_override
 
 library vm_references_test;
 
 import 'dart:mirrors';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 17 matching lines @@
   LibraryMirror libcore = expandoMirror.type.owner;
 
   var entries = expandoMirror.getField(MirrorSystem.getSymbol('_data', libcore)).reflectee;
   weak_property = entries.singleWhere((e) => e != null);
   print(weak_property);
 }
 
 var tests = [
 
 (Isolate isolate) =>
-  isolate.rootLib.load().then((Library lib) {
+  isolate.rootLibrary.load().then((Library lib) {
     Field keyField = lib.variables.singleWhere((v) => v.name == 'key');
     Instance key = keyField.value;
     Field valueField = lib.variables.singleWhere((v) => v.name == 'value');
     Instance value = valueField.value;
     Field propField = lib.variables.singleWhere((v) => v.name == 'weak_property');
     Instance prop = propField.value;
 
     expect(key.isWeakProperty, isFalse);
     expect(value.isWeakProperty, isFalse);
     expect(prop.isWeakProperty, isTrue);
     expect(prop.key, isNull);
     expect(prop.value, isNull);
     return prop.load().then((Instance loadedProp) {
       // Object ids are not cannonicalized, so we rely on the key and value
       // being the sole instances of their classes to test we got the objects
       // we expect.
       expect(loadedProp.key, isNotNull);
       expect(loadedProp.key.clazz, equals(key.clazz));
       expect(loadedProp.value, isNotNull);
       expect(loadedProp.value.clazz, equals(value.clazz));
     });
   }),
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);