Parallel marking.

runtime/vm/gc_marker.h

Index: runtime/vm/gc_marker.h
diff --git a/runtime/vm/gc_marker.h b/runtime/vm/gc_marker.h
index c01a6e8e5374a99de4cfbbccb55f0e9f777ebfa8..df7e0d2f3d9fae9e13d893d9eb657dbd1862f978 100644
--- a/runtime/vm/gc_marker.h
+++ b/runtime/vm/gc_marker.h
@@ -13,7 +13,6 @@ namespace dart {
 class HandleVisitor;
 class Heap;
 class Isolate;
-class MarkingVisitor;
 class ObjectPointerVisitor;
 class PageSpace;
 class RawWeakProperty;
@@ -38,16 +37,19 @@ class GCMarker : public ValueObject {
   void Epilogue(Isolate* isolate, bool invoke_api_callbacks);
   void IterateRoots(Isolate* isolate,
                     ObjectPointerVisitor* visitor,
-                    bool visit_prologue_weak_persistent_handles);
+                    bool visit_prologue_weak_persistent_handles,
+                    intptr_t slice_index, intptr_t num_slices);
   void IterateWeakRoots(Isolate* isolate,
                         HandleVisitor* visitor,
                         bool visit_prologue_weak_persistent_handles);
-  void IterateWeakReferences(Isolate* isolate, MarkingVisitor* visitor);
+  template<class MarkingVisitorType>
+  void IterateWeakReferences(Isolate* isolate, MarkingVisitorType* visitor);
   void ProcessWeakTables(PageSpace* page_space);
   void ProcessObjectIdTable(Isolate* isolate);
 
   // Called by anyone: finalize and accumulate stats from 'visitor'.
-  void FinalizeResultsFrom(MarkingVisitor* visitor);
+  template<class MarkingVisitorType>
+  void FinalizeResultsFrom(MarkingVisitorType* visitor);
 
   Heap* heap_;