First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/type_test_helper.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.
 
 library type_test_helper;
 
+import 'dart:async';
 import "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/dart_types.dart';
 import "parser_helper.dart" show SourceString;
 import "compiler_helper.dart";
 
 GenericType instantiate(TypeDeclarationElement element,
                         List<DartType> arguments) {
   if (element.isClass()) {
     return new InterfaceType(element, new Link<DartType>.fromList(arguments));
   } else {
     assert(element.isTypedef());
     return new TypedefType(element, new Link<DartType>.fromList(arguments));
   }
 }
 
 class TypeEnvironment {
   final MockCompiler compiler;
 
-  factory TypeEnvironment(String source) {
+  static Future<TypeEnvironment> create(String source) {
     var uri = new Uri(scheme: 'source');
     MockCompiler compiler = compilerFor('''
         main() {}
         $source''',
         uri,
         analyzeAll: true,
         analyzeOnly: true);
-    compiler.runCompiler(uri);
-    return new TypeEnvironment._(compiler);
+    return compiler.runCompiler(uri).then((_) {
+      return new TypeEnvironment._(compiler);
+    });
   }
 
   TypeEnvironment._(MockCompiler this.compiler);
 
   Element getElement(String name) {
     var element = findElement(compiler, name);
     Expect.isNotNull(element);
     if (element.isClass()) {
       element.ensureResolved(compiler);
     } else if (element.isTypedef()) {
@@ skipping 38 matching lines @@
         namedParameterNames.addLast(sourceString(name));
         namedParameterTypes.addLast(type);
       });
     }
     FunctionType type = new FunctionType(
         compiler.functionClass,
         returnType, parameterTypes, optionalParameterTypes,
         namedParameterNames.toLink(), namedParameterTypes.toLink());
   }
 }