Only evacuation candidate pages have a slots buffer, just visit these pages when filtering slots.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index dbb2d9c1fddb851a2838300bc93a3bd238a8edc5..49bf1040b0bbc8270470717cb2ed9878042a6e07 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -284,26 +284,13 @@ bool MarkCompactCollector::StartCompaction(CompactionMode mode) {
 }
 
 
-void MarkCompactCollector::ClearInvalidSlotsBufferEntries(PagedSpace* space) {
-  PageIterator it(space);
-  while (it.has_next()) {
-    Page* p = it.next();
-    SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer());
-  }
-}
-
-
 void MarkCompactCollector::ClearInvalidStoreAndSlotsBufferEntries() {
   heap_->store_buffer()->ClearInvalidStoreBufferEntries();
 
-  ClearInvalidSlotsBufferEntries(heap_->old_space());
-  ClearInvalidSlotsBufferEntries(heap_->code_space());
-  ClearInvalidSlotsBufferEntries(heap_->map_space());
-
-  LargeObjectIterator it(heap_->lo_space());
-  for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
-    MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
-    SlotsBuffer::RemoveInvalidSlots(heap_, chunk->slots_buffer());
+  int number_of_pages = evacuation_candidates_.length();
+  for (int i = 0; i < number_of_pages; i++) {
+    Page* p = evacuation_candidates_[i];
+    SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer());
   }
 }