Fixing analyzer error in polymer_expressions.

pkg/polymer_expressions/lib/expression.dart

Index: pkg/polymer_expressions/lib/expression.dart
diff --git a/pkg/polymer_expressions/lib/expression.dart b/pkg/polymer_expressions/lib/expression.dart
index e9c409a3fcc5422b21c9d152433602795d1909a8..0a5bb82e42e70d58da21aece657c3eed040a83f5 100644
--- a/pkg/polymer_expressions/lib/expression.dart
+++ b/pkg/polymer_expressions/lib/expression.dart
@@ -223,7 +223,7 @@ bool _listEquals(List a, List b) {
 
 int _hashList(List l) {
   var hash = l.fold(0,
-      (hash, item) => _JenkinsSmiHash.combine(hash, item.hashCode));
+      (h, item) => _JenkinsSmiHash.combine(h, item.hashCode));
   return _JenkinsSmiHash.finish(hash);
 }