Object.observe: Move notification of JSArray length changes to JSArray::SetElementsLength

test/mjsunit/harmony/object-observe.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 572 matching lines @@
 var array = {0: 1, 1: 2, 2: 3, length: 3};
 Object.observe(array, observer.callback);
 Array.prototype.splice.call(array, 1, 1, 4, 5);
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: array, name: '3', type: 'new' },
   { object: array, name: '1', type: 'updated', oldValue: 2 },
   { object: array, name: '2', type: 'updated', oldValue: 3 },
   { object: array, name: 'length', type: 'updated', oldValue: 3 },
 ]);
+
+// Exercise StoreIC_ArrayLength
+reset();
+var dummy = {};
+Object.observe(dummy, observer.callback);
+Object.unobserve(dummy, observer.callback);
+var array = [0];
+Object.observe(array, observer.callback);
+array.splice(0, 1);
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: array, name: '0', type: 'deleted', oldValue: 0 },
+  { object: array, name: 'length', type: 'updated', oldValue: 1},
+]);