Add List.shuffle().

sdk/lib/_internal/lib/js_array.dart

Index: sdk/lib/_internal/lib/js_array.dart
diff --git a/sdk/lib/_internal/lib/js_array.dart b/sdk/lib/_internal/lib/js_array.dart
index 5718c5d47314f6aca5154b2d5c99d27f2a76628f..b6ec0cbd4453d92e8170a17b0863b1781dcfc8de 100644
--- a/sdk/lib/_internal/lib/js_array.dart
+++ b/sdk/lib/_internal/lib/js_array.dart
@@ -243,6 +243,10 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
     IterableMixinWorkaround.sortList(this, compare);
   }
 
+  void shuffle() {
+    IterableMixinWorkaround.shuffleList(this);
+  }
+
   int indexOf(Object element, [int start = 0]) {
     return IterableMixinWorkaround.indexOfList(this, element, start);
   }