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

test/mjsunit/harmony/object-observe.js

Index: test/mjsunit/harmony/object-observe.js
diff --git a/test/mjsunit/harmony/object-observe.js b/test/mjsunit/harmony/object-observe.js
index dbdf84848d14e228e4a11a5ff4df4e6fd5a0cbcd..51a07aad4aa275f46fb5863cff440fcee9d4e413 100644
--- a/test/mjsunit/harmony/object-observe.js
+++ b/test/mjsunit/harmony/object-observe.js
@@ -590,3 +590,17 @@ observer.assertCallbackRecords([
   { 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},
+]);