Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/mirrors_used_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.
 
 /// Test that the @MirrorsUsed annotation suppress hints and that only
 /// requested elements are retained for reflection.
 library dart2js.test.mirrors_used_test;
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
@@ skipping 79 matching lines @@
     // We always include the names of some native classes.
     List<ClassElement> nativeClasses = [
       compiler.resolution.commonElements.intClass,
       compiler.resolution.commonElements.doubleClass,
       compiler.resolution.commonElements.numClass,
       compiler.resolution.commonElements.stringClass,
       compiler.resolution.commonElements.boolClass,
       compiler.resolution.commonElements.nullClass,
       compiler.resolution.commonElements.listClass
     ];
-    Iterable<String> nativeNames = nativeClasses.map(backend.namer.className);
+    Iterable<String> nativeNames =
+        // `backend.namer.className` returns a Name, but a String is required.
+        // ignore: ARGUMENT_TYPE_NOT_ASSIGNABLE
+        nativeClasses.map((c) => backend.namer.className(c));
     expectedNames = expectedNames.map(backend.namer.asName).toList();
     expectedNames.addAll(nativeNames);
 
     // Mirrors only work in the full emitter. We can thus be certain that the
     // emitter is the full emitter.
     full.Emitter fullEmitter = backend.emitter.emitter;
     Set recordedNames = new Set()
       ..addAll(fullEmitter.recordedMangledNames)
       ..addAll(fullEmitter.mangledFieldNames.keys)
       ..addAll(fullEmitter.mangledGlobalFieldNames.keys);
     Expect.setEquals(new Set.from(expectedNames), recordedNames);
 
-    for (var library in compiler.libraryLoader.libraries) {
+    for (dynamic library in compiler.libraryLoader.libraries) {
       library.forEachLocalMember((member) {
         if (member.isClass) {
           if (library == compiler.mainApp && member.name == 'Foo') {
             Expect.isTrue(
                 compiler.backend.mirrorsData
                     .isClassAccessibleByReflection(member),
                 '$member');
             member.forEachLocalMember((classMember) {
               Expect.isTrue(
                   compiler.backend.mirrorsData
@@ skipping 81 matching lines @@
 library lib;
 
 import 'dart:mirrors';
 
 useReflect(type) {
   print(new Symbol('Foo'));
   print(MirrorSystem.getName(reflectClass(type).owner.qualifiedName));
 }
 """,
 };