First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/no_duplicate_constructor_body_test.dart

Index: tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
diff --git a/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart b/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
index 3942536ef672f86efecc7671f9fcf3620e084403..205dbb0bd8b06b4c443f22ac5f56bc77365af26a 100644
--- a/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
+++ b/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
@@ -15,8 +15,9 @@ main() {
 """;
 
 main() {
-  String generated = compileAll(CODE);
-  RegExp regexp = new RegExp(r'\A: {"": "[A-za-z]+;"');
-  Iterator<Match> matches = regexp.allMatches(generated).iterator;
-  checkNumberOfMatches(matches, 1);
+  compileAll(CODE).then((generated) {
+    RegExp regexp = new RegExp(r'\A: {"": "[A-za-z]+;"');
+    Iterator<Match> matches = regexp.allMatches(generated).iterator;
+    checkNumberOfMatches(matches, 1);
+  });
 }