Make getKeys, getValues getters (keys, values).

utils/pub/yaml/visitor.dart

Index: utils/pub/yaml/visitor.dart
diff --git a/utils/pub/yaml/visitor.dart b/utils/pub/yaml/visitor.dart
index 744bcd7388e7be1f74170f06ce1b62f043db56a3..22ada8b2daabdddc3c10632188d2ab90afa32326 100644
--- a/utils/pub/yaml/visitor.dart
+++ b/utils/pub/yaml/visitor.dart
@@ -16,7 +16,7 @@ class _Visitor {
   /** Visits each key and value in [map] and returns a map of the results. */
   visitMapping(_MappingNode map) {
     var out = new YamlMap();
-    for (var key in map.content.getKeys()) {
+    for (var key in map.content.keys) {
       out[key.visit(this)] = map.content[key].visit(this);
     }
     return out;