Concurrent/parallel precise sweeping.

src/mark-compact.h

Index: src/mark-compact.h
diff --git a/src/mark-compact.h b/src/mark-compact.h
index 65167799ebc0afadb2741daeea83183ae78704cb..624f2b09a4a3e7d2483003584d53cfd82c731217 100644
--- a/src/mark-compact.h
+++ b/src/mark-compact.h
@@ -572,6 +572,8 @@ class MarkCompactCollector {
   enum SweeperType {
     PARALLEL_CONSERVATIVE,
     CONCURRENT_CONSERVATIVE,
+    PARALLEL_PRECISE,
+    CONCURRENT_PRECISE,
     PRECISE
   };
 
@@ -591,7 +593,7 @@ class MarkCompactCollector {
   // Sweep a single page from the given space conservatively.
   // Returns the size of the biggest continuous freed memory chunk in bytes.
   template<SweepingParallelism type>
-  static intptr_t SweepConservatively(PagedSpace* space,
+  static int SweepConservatively(PagedSpace* space,
                                       FreeList* free_list,
                                       Page* p);