Implementation of async-await transformation on js ast.

pkg/compiler/lib/src/js/template.dart

Index: pkg/compiler/lib/src/js/template.dart
diff --git a/pkg/compiler/lib/src/js/template.dart b/pkg/compiler/lib/src/js/template.dart
index ce57d09b8c7e2fe223d96c6d8cfcfc25f028c828..f08fe5239b4847576277eea271795f175b51ecae 100644
--- a/pkg/compiler/lib/src/js/template.dart
+++ b/pkg/compiler/lib/src/js/template.dart
@@ -435,6 +435,11 @@ class InstantiatorGeneratorVisitor implements NodeVisitor<Instantiator> {
     return (arguments) => new Return(makeExpression(arguments));
   }
 
+  Instantiator visitDartYield(DartYield node) {
+    Instantiator makeExpression = visit(node.expression);
+    return (arguments) => new DartYield(makeExpression(arguments), node.hasStar);
+  }
+
   Instantiator visitThrow(Throw node) {
     Instantiator makeExpression = visit(node.expression);
     return (arguments) => new Throw(makeExpression(arguments));
@@ -487,8 +492,11 @@ class InstantiatorGeneratorVisitor implements NodeVisitor<Instantiator> {
         new FunctionDeclaration(makeName(arguments), makeFunction(arguments));
   }
 
-  Instantiator visitLabeledStatement(LabeledStatement node) =>
-      TODO('visitLabeledStatement');
+  Instantiator visitLabeledStatement(LabeledStatement node) {
+    Instantiator makeBody = visit(node.body);
+    return (arguments) => new LabeledStatement(node.label, makeBody(arguments));
+  }
+
   Instantiator visitLiteralStatement(LiteralStatement node) =>
       TODO('visitLiteralStatement');
   Instantiator visitBlob(Blob node) =>