First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/simple_inferrer_final_field3_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 we are analyzing field parameters correctly.
 
 import 'package:expect/expect.dart';
+import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
 
 const String TEST = """
 
 class A {
   final dynamicField;
   A() : dynamicField = 42;
   A.bar(this.dynamicField);
 }
 
 main() {
   new A();
   new A.bar('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;
 
-  checkFieldTypeInClass(String className, String fieldName, type) {
-    var cls = findElement(compiler, className);
-    var element = cls.lookupLocalMember(buildSourceString(fieldName));
-    Expect.equals(type,
-        typesInferrer.getTypeOfElement(element).simplify(compiler));
-  }
+    checkFieldTypeInClass(String className, String fieldName, type) {
+      var cls = findElement(compiler, className);
+      var element = cls.lookupLocalMember(buildSourceString(fieldName));
+      Expect.equals(type,
+          typesInferrer.getTypeOfElement(element).simplify(compiler));
+    }
 
-  checkFieldTypeInClass('A', 'dynamicField',
-      findTypeMask(compiler, 'Interceptor', 'nonNullSubclass'));
+    checkFieldTypeInClass('A', 'dynamicField',
+        findTypeMask(compiler, 'Interceptor', 'nonNullSubclass'));
+  }));
 }