Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/override_inheritance_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.
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'compiler_helper.dart';
 import 'package:compiler/src/resolution/class_members.dart' show MembersCreator;
 
 main() {
   asyncTest(() => Future.wait([
         testRequiredParameters(),
         testPositionalParameters(),
         testNamedParameters(),
         testNotSubtype(),
         testGetterNotSubtype(),
         testSetterNotSubtype(),
         testGenericNotSubtype(),
         testFieldNotSubtype(),
         testMixedOverride(),
         testAbstractMethods(),
         testNoSuchMethod(),
       ]));
 }
 
 Future check(String source, {errors, warnings, hints, infos}) {
   return MockCompiler.create((MockCompiler compiler) {
     compiler.diagnosticHandler = createHandler(compiler, source);
     compiler.parseScript(source);
-    var mainApp = compiler.mainApp;
+    dynamic mainApp = compiler.mainApp;
     var cls = mainApp.find('Class');
     cls.ensureResolved(compiler.resolution);
     MembersCreator.computeAllClassMembers(compiler.resolution, cls);
 
     toList(o) => o == null ? [] : o is List ? o : [o];
 
     compareMessageKinds(
         source, toList(errors), compiler.diagnosticCollector.errors, 'error');
 
     compareMessageKinds(source, toList(warnings),
@@ skipping 1651 matching lines @@
     check("""
           class A {
             noSuchMethod(_) => null;
             method(); // testNoSuchMethod:13
           }
           class Class extends A {
           }
           """),
   ]);
 }