Make (Object.)observed Arrays use SafeRemoveArrayHoles during sort

test/mjsunit/harmony/object-observe.js

Index: test/mjsunit/harmony/object-observe.js
diff --git a/test/mjsunit/harmony/object-observe.js b/test/mjsunit/harmony/object-observe.js
index 372ffdbdb7068240dfd441dd28baba2f5209d22b..47b5d8cd5e47575c783713a4afe180343626ff6c 100644
--- a/test/mjsunit/harmony/object-observe.js
+++ b/test/mjsunit/harmony/object-observe.js
@@ -1142,6 +1142,22 @@ observer.assertCallbackRecords([
   { object: array, name: '2', type: 'updated', oldValue: 3 },
 ]);
 
+// Sort
+reset();
+var array = [3, 2, 1];
+Object.observe(array, observer.callback);
+array.sort();
+assertEquals(1, array[0]);
+assertEquals(2, array[1]);
+assertEquals(3, array[2]);
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: array, name: '1', type: 'updated', oldValue: 2 },
+  { object: array, name: '0', type: 'updated', oldValue: 3 },
+  { object: array, name: '2', type: 'updated', oldValue: 1 },
+  { object: array, name: '1', type: 'updated', oldValue: 3 },
+  { object: array, name: '0', type: 'updated', oldValue: 2 },
+]);
 
 //
 // === PLAIN OBJECTS ===