Implement tracking and optimizations of packed arrays

test/mjsunit/regress/regress-smi-only-concat.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 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --allow-natives-syntax
 
 // This tests that concatenating a fast smi-only array and a fast object array
 // results in a fast object array.
 
 var fast_array = ['a', 'b'];
 var array = fast_array.concat(fast_array);
 
-assertTrue(%HasFastElements(fast_array));
-assertTrue(%HasFastElements(array));
+assertTrue(%HasFastObjectElements(fast_array));
+assertTrue(%HasFastObjectElements(array));