Use heap iterator in store buffer when page was swept precisely.

src/store-buffer.cc

Index: src/store-buffer.cc
diff --git a/src/store-buffer.cc b/src/store-buffer.cc
index d1a04d292fb2cb0f79282972caa0b26c8d3b8c2f..dbd9cc7415e04b47bf57f3aedf8143ff3dfb9930 100644
--- a/src/store-buffer.cc
+++ b/src/store-buffer.cc
@@ -515,8 +515,25 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
                 heap_->mark_compact_collector()->EnsureSweepingCompleted();
               }
             }
-            FindPointersToNewSpaceInRegion(
-                start, end, slot_callback, clear_maps);
+            // TODO(hpayer): remove the special casing and merge map and pointer
+            // space handling as soon as we removed conservative sweeping.
+            CHECK(page->owner() == heap_->old_pointer_space());
+            if (heap_->old_pointer_space()->swept_precisely()) {
+              HeapObjectIterator iterator(page, NULL);
+              for (HeapObject* heap_object = iterator.Next();
+                   heap_object != NULL; heap_object = iterator.Next()) {
+                // We iterate over objects that contain new space pointers only.
+                if (heap_object->MayContainNewSpacePointers()) {
+                  FindPointersToNewSpaceInRegion(
+                      heap_object->address() + HeapObject::kHeaderSize,
+                      heap_object->address() + heap_object->Size(),
+                      slot_callback, clear_maps);
+                }
+              }
+            } else {
+              FindPointersToNewSpaceInRegion(start, end, slot_callback,
+                                             clear_maps);
+            }
           }
         }
       }