Use the incremental root marking visitor for overapproximating the weak closure

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 29cf00e9757922789a908ccf24080fd296db8636..f23f86b442d317cb7337a3bebdf2fc63467e2291 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -2228,9 +2228,12 @@ void MarkCompactCollector::OverApproximateWeakClosure() {
   GCTracer::Scope gc_scope(heap()->tracer(),
                            GCTracer::Scope::MC_INCREMENTAL_WEAKCLOSURE);
 
-  RootMarkingVisitor root_visitor(heap());
+  ObjectVisitor* root_visitor =
+      heap()->incremental_marking()->CreateRootMarkingVisitor();

[Hannes Payer (out of office), 2015/03/12 12:28:48]

Instead of allocating the incremental root marking visitor and deallocating it
later (and leaking it to a different context), why don't you create a method in
incremental marking that incrementally marks the object groups with a stack
allocated visitor?

Hmm, wait, it feels like this method should be part of incremental marking. Can
we move it there?

   isolate()->global_handles()->IterateObjectGroups(
-      &root_visitor, &IsUnmarkedHeapObjectWithHeap);
+      root_visitor, &IsUnmarkedHeapObjectWithHeap);
+  delete root_visitor;
+
   MarkImplicitRefGroups();
 
   // Remove object groups after marking phase.