Make Map.keys/values Iterables.

utils/pub/yaml/yaml_map.dart

Index: utils/pub/yaml/yaml_map.dart
diff --git a/utils/pub/yaml/yaml_map.dart b/utils/pub/yaml/yaml_map.dart
index e80a98836a98a50a78a5c1ef51c090a519b69113..65dd11994f04684fa039b946fd65d1d861455534 100644
--- a/utils/pub/yaml/yaml_map.dart
+++ b/utils/pub/yaml/yaml_map.dart
@@ -29,8 +29,8 @@ class YamlMap implements Map {
   void clear() => _map.clear();
   void forEach(void f(key, value)) =>
     _map.forEach((k, v) => f(_unwrapKey(k), v));
-  Collection get keys => _map.keys.mappedBy(_unwrapKey).toList();
-  Collection get values => _map.values;
+  Iterable get keys => _map.keys.mappedBy(_unwrapKey);
+  Iterable get values => _map.values;
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   String toString() => _map.toString();
@@ -94,7 +94,7 @@ int _hashCode(obj, [List parents]) {
       return _hashCode(obj.keys, parents) ^
         _hashCode(obj.values, parents);
     }
-    if (obj is List) {
+    if (obj is Iterable) {
       // This is probably a really bad hash function, but presumably we'll get
       // this in the standard library before it actually matters.
       int hash = 0;