First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/simple_inferrer_unregister_call_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.
 
 import 'package:expect/expect.dart';
-
+import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
 
 const String TEST = """
 var a = '';
 class A {
   operator+(other) => other;
 }
 
 foo() {
   // The following '+' call will first say that it may call A::+,
   // String::+, or int::+. After all methods have been analyzed, we know
   // that a is of type String, and therefore, this method cannot call
   // A::+. Therefore, the type of the parameter of A::+ will be the
   // one given by the other calls.
   return a + 'foo';
 }
 
 main() {
   new A() + 42;
   foo();
 }
 """;
 
 
 void main() {
   Uri uri = new Uri(scheme: 'source');
   var compiler = compilerFor(TEST, uri);
-  compiler.runCompiler(uri);
-  var typesInferrer = compiler.typesTask.typesInferrer;
+  asyncTest(() => compiler.runCompiler(uri).then((_) {
+    var typesInferrer = compiler.typesTask.typesInferrer;
 
-  checkReturnInClass(String className, String methodName, type) {
-    var cls = findElement(compiler, className);
-    var element = cls.lookupLocalMember(buildSourceString(methodName));
-    Expect.equals(type, typesInferrer.getReturnTypeOfElement(element));
-  }
+    checkReturnInClass(String className, String methodName, type) {
+      var cls = findElement(compiler, className);
+      var element = cls.lookupLocalMember(buildSourceString(methodName));
+      Expect.equals(type, typesInferrer.getReturnTypeOfElement(element));
+    }
 
-  checkReturnInClass('A', '+', compiler.typesTask.intType);
+    checkReturnInClass('A', '+', compiler.typesTask.intType);
+  }));
 }