Reland of move more dead code after Object.observe removal

src/js/array.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 1006 matching lines @@
     // The specification allows "implementation dependent" behavior
     // if an element on the prototype chain has an element that
     // might interact with sorting.
     max_prototype_element = CopyFromPrototype(array, length);
   }
 
   // %RemoveArrayHoles returns -1 if fast removal is not supported.
   var num_non_undefined = %RemoveArrayHoles(array, length);
 
   if (num_non_undefined == -1) {
-    // The array is observed, or there were indexed accessors in the array.
+    // There were indexed accessors in the array.
     // Move array holes and undefineds to the end using a Javascript function
-    // that is safe in the presence of accessors and is observable.
+    // that is safe in the presence of accessors.
     num_non_undefined = SafeRemoveArrayHoles(array);
   }
 
   QuickSort(array, 0, num_non_undefined);
 
   if (!is_array && (num_non_undefined + 1 < max_prototype_element)) {
     // For compatibility with JSC, we shadow any elements in the prototype
     // chain that has become exposed by sort moving a hole to its position.
     ShadowPrototypeElements(array, num_non_undefined, max_prototype_element);
   }
@@ skipping 754 matching lines @@
 %InstallToContext([
   "array_pop", ArrayPop,
   "array_push", ArrayPush,
   "array_shift", ArrayShift,
   "array_splice", ArraySplice,
   "array_slice", ArraySlice,
   "array_unshift", ArrayUnshift,
 ]);
 
 });