Eliminate uses of fuzzy arrows in pkg/testing (fix bots).

pkg/testing/lib/src/expectation.dart

 // Copyright (c) 2017, 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.md file.
 
 library testing.expectation;
 
 /// An expectation represents the expected outcome of a test (or if it should
 /// be skipped).
 ///
 /// An expectation belongs to a group, for example, [ExpectationGroup.Fail].
@@ skipping 71 matching lines @@
     return internalMap[name.toLowerCase()] ??
         (throw "No expectation named: '$name'.");
   }
 
   factory ExpectationSet.fromJsonList(List data) {
     Map<String, Expectation> internalMap =
         new Map<String, Expectation>.from(Default.internalMap);
     for (Map map in data) {
       String name;
       String group;
-      map.forEach((String key, String value) {
+      map.forEach((_key, _value) {
+        String key = _key;
+        String value = _value;
         switch (key) {
           case "name":
             name = value;
             break;
 
           case "group":
             group = value;
             break;
 
           default:
@@ skipping 37 matching lines @@
     case "Pass":
       return ExpectationGroup.Pass;
     case "Skip":
       return ExpectationGroup.Skip;
     case "Timeout":
       return ExpectationGroup.Timeout;
     default:
       throw "Unrecognized group: '$name'.";
   }
 }