Support async/await in the dart2js frontend.

tests/compiler/dart2js/backend_dart/dart_printer_test.dart

Index: tests/compiler/dart2js/backend_dart/dart_printer_test.dart
diff --git a/tests/compiler/dart2js/backend_dart/dart_printer_test.dart b/tests/compiler/dart2js/backend_dart/dart_printer_test.dart
index 180870f6804fceda58b94d9cbbc7e649dde638c6..f2780808b83014c277652a445512b37cd4d7a528 100644
--- a/tests/compiler/dart2js/backend_dart/dart_printer_test.dart
+++ b/tests/compiler/dart2js/backend_dart/dart_printer_test.dart
@@ -417,11 +417,13 @@ class AstBuilder extends Listener {
   handleNoFormalParameters(tok) {
     push(new Parameters([]));
   }
-  endUnamedFunction(t) {
+
+  endUnnamedFunction(t) {
     Statement body = pop();
     Parameters parameters = pop();
     push(new FunctionExpression(parameters, body));
   }
+
   handleNoType(Token token) {
     push(null);
   }
@@ -572,7 +574,7 @@ class AstBuilder extends Listener {
     push(null);
   }
 
-  endForIn(Token begin, Token inKeyword, Token end) {
+  endForIn(Token await, Token begin, Token inKeyword, Token end) {
     Statement body = pop();
     Expression exp = pop();
     Node declaredIdentifier = pop();