Fix strong mode warnings.

test/wrapper_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.
 
 /// Tests wrapper utilities.
 
 import "dart:collection";
 import "package:collection/collection.dart";
 import "package:test/test.dart";
 
@@ skipping 67 matching lines @@
   noSuchMethod(Invocation i) => _action(i);
 }
 
 const TO_STRING_INVOCATION = const SyntheticInvocation(
   #toString, const[], const{}, SyntheticInvocation.METHOD);
 
 // LikeNSM, but has types Iterable, Set and List to allow it as
 // argument to DelegatingIterable/Set/List.
 class IterableNSM extends NSM implements Iterable, Set, List, Queue {
   IterableNSM(action(Invocation i)) : super(action);
-  noSuchMethod(Invocation i) => super.noSuchMethod(i);  // Silence warnings
   toString() => super.noSuchMethod(TO_STRING_INVOCATION);
 }
 
 // Expector that wraps in DelegatingIterable.
 class IterableExpector extends Expector {
   getWrappedObject(void action(Invocation i)) {
     return new DelegatingIterable(new IterableNSM(action));
   }
 }
 
@@ skipping 14 matching lines @@
 // Expector that wraps in DelegatingSet.
 class QueueExpector extends Expector {
   getWrappedObject(void action(Invocation i)) {
     return new DelegatingQueue(new IterableNSM(action));
   }
 }
 
 // Like NSM but implements Map to allow as argument for DelegatingMap.
 class MapNSM extends NSM implements Map {
   MapNSM(action(Invocation i)) : super(action);
-  noSuchMethod(Invocation i) => super.noSuchMethod(i);
   toString() => super.noSuchMethod(TO_STRING_INVOCATION);
 }
 
 // Expector that wraps in DelegatingMap.
 class MapExpector extends Expector {
   getWrappedObject(void action(Invocation i)) {
     return new DelegatingMap(new MapNSM(action));
   }
 }
 
@@ skipping 521 matching lines @@
 
     test(".retainWhere", () {
       map["f"] = "foo";
       map["b"] = "bar";
       map["q"] = "qoo";
       set.retainWhere((element) => element.endsWith("o"));
       expect(map, equals({"f": "foo", "q": "qoo"}));
     });
   });
 }