Ensure CopyElementsImpl is always executed so it fills in holes even if from_size is 0. Allow Fixed…

test/mjsunit/array-store-and-grow.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 81 matching lines @@
 
 function array_store_5(a,b,c) {
   return (a[b] = c);
 }
 
 a = makeCOW();
 array_store_5(a, 1, 0.5);
 a = makeCOW();
 array_store_5(a, 1, 0.5);
 assertEquals(0.5, a[1]);
-assertEquals(0.5, array_store_5([], 1, 0.5));
+a = [];
+assertEquals(0.5, array_store_5(a, 1, 0.5));
+assertEquals(undefined, a[0]);
+assertEquals(0.5, a[1]);
 
 function array_store_6(a,b,c) {
   return (a[b] = c);
 }
 
 a = makeCOW();
 array_store_6(a, 1, x);
 a = makeCOW();
 array_store_6(a, 1, x);
 assertEquals(x, a[1]);
@@ skipping 61 matching lines @@
 function array_store_9(a,b,c) {
   return (a[b] = c);
 }
 
 var a = [];
 array_store_9(a, 0, 0.5);
 a = [];
 array_store_1(a, 0, 0.5);
 assertEquals(0.5, a[0]);
 assertEquals(0.5, array_store_1([], 0, 0.5));