All strong mode cleaning of dart2js.

tests/compiler/dart2js/bad_output_io_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 compiler can handle imports when package root has not been set.
 
 library dart2js.test.bad_output_io;
 
+import 'dart:async' show Future;
 import 'dart:io' show exit;
 import 'package:expect/expect.dart';
 
 import 'package:compiler/compiler.dart' show Diagnostic;
 import 'package:compiler/compiler_new.dart'
-    show CompilerDiagnostics, CompilerInput, CompilerOutput, OutputType;
+    show
+        CompilationResult,
+        CompilerDiagnostics,
+        CompilerInput,
+        CompilerOutput,
+        OutputType;
 import 'package:compiler/src/dart2js.dart'
     show exitFunc, compileFunc, compile, diagnosticHandler;
 import 'package:compiler/src/source_file_provider.dart'
     show FormattingDiagnosticHandler;
 
 import 'package:compiler/src/options.dart' show CompilerOptions;
 
 class CollectingFormattingDiagnosticHandler
     implements FormattingDiagnosticHandler {
   final provider = null;
@@ skipping 26 matching lines @@
 
   String prefixMessage(String message, Diagnostic kind) {
     return message;
   }
 
   int fatalCount;
 
   int throwOnErrorCount;
 }
 
-testOutputProvider(CompilerOptions options, CompilerInput input,
-    CompilerDiagnostics diagnostics, CompilerOutput output) {
+Future<CompilationResult> testOutputProvider(
+    CompilerOptions options,
+    CompilerInput input,
+    CompilerDiagnostics diagnostics,
+    CompilerOutput output) {
   diagnosticHandler = new CollectingFormattingDiagnosticHandler();
   output.createOutputSink(
       "/non/existing/directory/should/fail/file", "js", OutputType.js);
+  return null;
 }
 
 void main() {
   compileFunc = testOutputProvider;
   exitFunc = (exitCode) {
     CollectingFormattingDiagnosticHandler handler = diagnosticHandler;
     Expect.equals(1, handler.messages.length);
     var message = handler.messages[0];
     Expect.isTrue(message[0].contains("Cannot open file"));
     Expect.equals(Diagnostic.ERROR, message[1]);
     Expect.equals(1, exitCode);
     exit(0);
   };
   compile(["foo.dart", "--out=bar.dart"]);
 }