JS parser: fixed labelled break/continue

js/js.dart-ast/src/com/google/dart/compiler/util/AstUtil.java

@@ -52,4 +52,12 @@ public final class AstUtil {
 
         return nodesCopy;
     }
+
+    @NotNull
+    public static JsFunctionScope toFunctionScope(JsScope scope) {
+        assert scope instanceof JsFunctionScope: "JsFunctionScope type is expected, but "
+                                                 + scope.getClass().getSimpleName() + " is found";
+
+        return (JsFunctionScope) scope;
+    }
 }