support class native clause

pkg/compiler/lib/src/parser/element_listener.dart

Index: pkg/compiler/lib/src/parser/element_listener.dart
diff --git a/pkg/compiler/lib/src/parser/element_listener.dart b/pkg/compiler/lib/src/parser/element_listener.dart
index 964d1dba7fb912c45d0e0e3afe7bdc8ad945fa67..e755c3c626d7b904a6bdff4fac2621ef3126fc2a 100644
--- a/pkg/compiler/lib/src/parser/element_listener.dart
+++ b/pkg/compiler/lib/src/parser/element_listener.dart
@@ -285,7 +285,11 @@ class ElementListener extends Listener {
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
+      Token nativeToken,
       Token endToken) {
+    if (nativeToken?.next?.type == TokenType.STRING) {
+      popNode(); // native clause - LiteralString

[ahe, 2017/08/21 12:04:10]

Same comment as in ast_builder.dart:

I would expect this:

if (nativeToken != null) {
  popNode(); // Native clause, a LiteralString.
}

[danrubel, 2017/08/22 01:35:28]

Yup. Fixed as described earlier.

+    }
     makeNodeList(interfacesCount, implementsKeyword, null, ","); // interfaces
     popNode(); // superType
     popNode(); // typeParameters