Merge r7706 from the bleeding_edge into 3.1 branch....

test/mjsunit/regress/splice-missing-wb.js

 // Copyright 2011 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 36 matching lines @@
 a.splice(2, 200);
 
 // Force gc and heap verification.
 gc();
 
 // Try accessing a[0].idx. It will segfault if write-barrier was accidentally
 // omitted.
 assertEquals(0, a[0].idx);
 assertEquals(1, a[1].idx);
 assertEquals(202, a[2].idx);