Repeatedly overapproximate the weak closure as long as we make progress

src/heap/incremental-marking.h

Index: src/heap/incremental-marking.h
diff --git a/src/heap/incremental-marking.h b/src/heap/incremental-marking.h
index 21fdb2da3735b1cf5ff67f712ecc71e71a2c1c3f..0d4a81a1b464bbc41ef4bde9f78a48d3c2227291 100644
--- a/src/heap/incremental-marking.h
+++ b/src/heap/incremental-marking.h
@@ -41,9 +41,6 @@ class IncrementalMarking {
   bool weak_closure_was_overapproximated() const {
     return weak_closure_was_overapproximated_;
   }
-  void set_weak_closure_was_overapproximated(bool val) {
-    weak_closure_was_overapproximated_ = val;
-  }
 
   inline bool IsStopped() { return state() == STOPPED; }
 
@@ -249,6 +246,8 @@ class IncrementalMarking {
 
   bool weak_closure_was_overapproximated_;
 
+  int weak_closure_approximation_rounds_;
+
   GCRequestType request_type_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);