First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/simple_inferrer_final_field3_test.dart

Index: tests/compiler/dart2js/simple_inferrer_final_field3_test.dart
diff --git a/tests/compiler/dart2js/simple_inferrer_final_field3_test.dart b/tests/compiler/dart2js/simple_inferrer_final_field3_test.dart
index 058187bfb70857ef71f0743571be10cc3246f843..7b6e077b454f5b79bff22b5341d6644ed9e55da2 100644
--- a/tests/compiler/dart2js/simple_inferrer_final_field3_test.dart
+++ b/tests/compiler/dart2js/simple_inferrer_final_field3_test.dart
@@ -25,16 +25,17 @@ main() {
 void main() {
   Uri uri = new Uri(scheme: 'source');
   var compiler = compilerFor(TEST, uri);
-  compiler.runCompiler(uri);
-  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.internal.typeOf[element].simplify(compiler));
-  }
-
-  checkFieldTypeInClass('A', 'dynamicField',
-      findTypeMask(compiler, 'Interceptor', 'nonNullSubclass'));
+  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.internal.typeOf[element].simplify(compiler));
+    }
+
+    checkFieldTypeInClass('A', 'dynamicField',
+        findTypeMask(compiler, 'Interceptor', 'nonNullSubclass'));
+  });
 }