Allow partial scanning of large arrays in order to avoid

src/mark-compact-inl.h

Index: src/mark-compact-inl.h
===================================================================
--- src/mark-compact-inl.h	(revision 12609)
+++ src/mark-compact-inl.h	(working copy)
@@ -83,6 +83,9 @@
                                       Object** slot,
                                       Object* object) {
   Page* object_page = Page::FromAddress(reinterpret_cast<Address>(object));
+  // Ensure the anchor slot is on the first 'page' of a large object.
+  ASSERT(Page::FromAddress(reinterpret_cast<Address>(anchor_slot))->owner() !=
+         NULL);
   if (object_page->IsEvacuationCandidate() &&
       !ShouldSkipEvacuationSlotRecording(anchor_slot)) {
     if (!SlotsBuffer::AddTo(&slots_buffer_allocator_,