Visit encountered JSWeakCollection list during scavenging.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_H_
 #define V8_HEAP_H_
 
 #include <cmath>
 
 #include "allocation.h"
@@ skipping 831 matching lines @@
   void set_allocation_sites_list(Object* object) {
     allocation_sites_list_ = object;
   }
   Object* allocation_sites_list() { return allocation_sites_list_; }
 
   // Used in CreateAllocationSiteStub and the (de)serializer.
   Object** allocation_sites_list_address() { return &allocation_sites_list_; }
 
   Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
 
+  void set_encountered_weak_collections(Object* weak_collection) {
+    encountered_weak_collections_ = weak_collection;
+  }
+  Object* encountered_weak_collections() const {
+    return encountered_weak_collections_;
+  }
+
   // Number of mark-sweeps.
   unsigned int ms_count() { return ms_count_; }
 
   // Iterates over all roots in the heap.
   void IterateRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all strong roots in the heap.
   void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over entries in the smi roots list.  Only interesting to the
   // serializer/deserializer, since GC does not care about smis.
   void IterateSmiRoots(ObjectVisitor* v);
@@ skipping 736 matching lines @@
   // List heads are initilized lazily and contain the undefined_value at start.
   Object* native_contexts_list_;
   Object* array_buffers_list_;
   Object* allocation_sites_list_;
 
   // WeakHashTable that maps objects embedded in optimized code to dependent
   // code list. It is initilized lazily and contains the undefined_value at
   // start.
   Object* weak_object_to_code_table_;
 
+  // List of encountered weak collections (JSWeakMap and JSWeakSet) during
+  // marking. It is initialized during marking, destroyed after marking and
+  // contains Smi(0) while marking is not active.
+  Object* encountered_weak_collections_;
+
   StoreBufferRebuilder store_buffer_rebuilder_;
 
   struct StringTypeTable {
     InstanceType type;
     int size;
     RootListIndex index;
   };
 
   struct ConstantStringTable {
     const char* contents;
@@ skipping 1143 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_