Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/in_user_code_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.
 
 // Test that the helper [Compiler.inUserCode] works as intended.
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/commandline_options.dart';
@@ skipping 30 matching lines @@
 };
 
 Future test(List<Uri> entryPoints, Map<String, bool> expectedResults) async {
   CompilationResult result = await runCompiler(
       entryPoints: entryPoints,
       memorySourceFiles: SOURCE,
       options: [Flags.analyzeOnly, Flags.analyzeAll],
       packageRoot: Uri.parse('memory:pkg/'));
   Compiler compiler = result.compiler;
   expectedResults.forEach((String uri, bool expectedResult) {
-    var element = compiler.libraryLoader.lookupLibrary(Uri.parse(uri));
+    dynamic element = compiler.libraryLoader.lookupLibrary(Uri.parse(uri));
     Expect.isNotNull(element, "Unknown library '$uri'.");
     Expect.equals(
         expectedResult,
         compiler.inUserCode(element),
         expectedResult
             ? "Library '$uri' expected to be in user code"
             : "Library '$uri' not expected to be in user code");
   });
 }
 
@@ skipping 38 matching lines @@
     Uri.parse('dart:async'),
     Uri.parse('package:sub/bar.dart')
   ], {
     'package:sub/bar.dart': true,
     'package:sub/baz.dart': true,
     'package:sup/boz.dart': false,
     'dart:core': true,
     'dart:async': true
   });
 }