Fix x64 build.

src/heap.cc

Index: src/heap.cc
===================================================================
--- src/heap.cc	(revision 2413)
+++ src/heap.cc	(working copy)
@@ -670,7 +670,7 @@
 
   HeapObjectIterator cell_iterator(cell_space_);
   while (cell_iterator.has_next()) {
-    cell_iterator.next()->Iterate(&scavenge_visitor));
+    cell_iterator.next()->Iterate(&scavenge_visitor);
   }
 
   HeapObjectIterator map_iterator(map_space_);