Decoupling MarkDescriptorArray as much as possible from the ContentArray.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 4e4fb385b966f7f5949a35a7e2ad1e8ad9fed9c1..ca290780fca6aa1f85ffdb8c1e1fbb10b5054be4 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -5838,7 +5838,11 @@ MaybeObject* DescriptorArray::RemoveTransitions() {
   return new_descriptors;
 }
 
-
+// We need the whiteness witness since sort will reshuffle the entries in the
+// descriptor array. If the descriptor array were to be gray, the sort would
+// potentially swap a black and a white member. This would resulting in

[Michael Starzinger, 2012/05/24 14:28:54]

Reasoning is off.

[...] were to be black, the shuffling would move a slot that was already
recorded as pointing into an evacuation candidate. This would result in missing
updates upon evacuation.

[Toon Verwaest, 2012/05/25 12:27:26]

Done.

+// accidentally reclaiming the white member if the descriptor array owned the
+// unique pointer.
 void DescriptorArray::SortUnchecked(const WhitenessWitness& witness) {
   // In-place heap sort.
   int len = number_of_descriptors();