Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/expect_annotations2_test.dart

 // Copyright (c) 2012, 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 "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import 'package:compiler/compiler_new.dart';
 import 'memory_compiler.dart';
 
 const MEMORY_SOURCE_FILES = const {
@@ skipping 20 matching lines @@
           print(foo(23412));
           print(A.bar(87654));
           print(new A().gee(1337, 919182));
           print(new A().field + 1);
         }'''
 };
 
 void main() {
   asyncTest(() async {
     OutputCollector collector = new OutputCollector();
-    CompilationResult result = await runCompiler(
+    await runCompiler(
         memorySourceFiles: MEMORY_SOURCE_FILES, outputProvider: collector);
     // Simply check that the constants of the small functions are still in the
     // output, and that we don't see the result of constant folding.
     String jsOutput = collector.getOutput('', OutputType.js);
 
     Expect.isTrue(jsOutput.contains('49912344'));
     Expect.isTrue(jsOutput.contains('123455'));
     Expect.isTrue(jsOutput.contains('81234512'));
     Expect.isFalse(jsOutput.contains('49935756'));
     Expect.isFalse(jsOutput.contains('211109'));
     Expect.isFalse(jsOutput.contains('82155031'));
     Expect.isFalse(jsOutput.contains('4712'));
   });
 }