Make (Object.)observed Arrays use SafeRemoveArrayHoles during sort

R=adamk,rossberg
BUG=

Review URL: https://codereview.chromium.org/15837006

Patch from Rafael Weinstein <rafaelw@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14847 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/array.js

@@ -1110,11 +1110,13 @@ function ArraySort(comparefn) {
     max_prototype_element = CopyFromPrototype(this, length);
   }
 
-  var num_non_undefined = %RemoveArrayHoles(this, length);
+  var num_non_undefined = %IsObserved(this) ?
+      -1 : %RemoveArrayHoles(this, length);
+
   if (num_non_undefined == -1) {
-    // There were indexed accessors in the array.  Move array holes and
-    // undefineds to the end using a Javascript function that is safe
-    // in the presence of accessors.
+    // The array is observed, or there were indexed accessors in the array.
+    // Move array holes and undefineds to the end using a Javascript function
+    // that is safe in the presence of accessors and is observable.
     num_non_undefined = SafeRemoveArrayHoles(this);
   }
 

src/objects.cc

@@ -13758,12 +13758,13 @@ MaybeObject* JSObject::PrepareSlowElementsForSort(uint32_t limit) {
 MaybeObject* JSObject::PrepareElementsForSort(uint32_t limit) {
   Heap* heap = GetHeap();
 
+  ASSERT(!map()->is_observed());
   if (HasDictionaryElements()) {
     // Convert to fast elements containing only the existing properties.
     // Ordering is irrelevant, since we are going to sort anyway.
     SeededNumberDictionary* dict = element_dictionary();
     if (IsJSArray() || dict->requires_slow_elements() ||
-        dict->max_number_key() >= limit || map()->is_observed()) {
+        dict->max_number_key() >= limit) {
       return PrepareSlowElementsForSort(limit);
     }
     // Convert to fast elements.

test/mjsunit/harmony/object-observe.js

@@ -1142,6 +1142,22 @@ observer.assertCallbackRecords([
   { object: array, name: '2', type: 'updated', oldValue: 3 },
 ]);
 
+// Sort
+reset();
+var array = [3, 2, 1];
+Object.observe(array, observer.callback);
+array.sort();
+assertEquals(1, array[0]);
+assertEquals(2, array[1]);
+assertEquals(3, array[2]);
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: array, name: '1', type: 'updated', oldValue: 2 },
+  { object: array, name: '0', type: 'updated', oldValue: 3 },
+  { object: array, name: '2', type: 'updated', oldValue: 1 },
+  { object: array, name: '1', type: 'updated', oldValue: 3 },
+  { object: array, name: '0', type: 'updated', oldValue: 2 },
+]);
 
 //
 // === PLAIN OBJECTS ===