Merged r19848 into 3.24 branch.

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index 372b7ece6382118a7a578e9a2d0f40ac43ae222a..03c679a44ed74a07dcb58ad7a9bd7b5eb0041404 100644
--- a/src/array.js
+++ b/src/array.js
@@ -1115,8 +1115,8 @@ function ArraySort(comparefn) {
     max_prototype_element = CopyFromPrototype(this, length);
   }
 
-  var num_non_undefined = %IsObserved(this) ?
-      -1 : %RemoveArrayHoles(this, length);
+  // %RemoveArrayHoles returns -1 if fast removal is not supported.
+  var num_non_undefined = %RemoveArrayHoles(this, length);
 
   if (num_non_undefined == -1) {
     // The array is observed, or there were indexed accessors in the array.