Make incremental marker post-process JSWeakCollection.

test/cctest/test-weakmaps.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 28 matching lines @@
 static Isolate* GetIsolateFrom(LocalContext* context) {
   return reinterpret_cast<Isolate*>((*context)->GetIsolate());
 }
 
 
 static Handle<JSWeakMap> AllocateJSWeakMap(Isolate* isolate) {
   Factory* factory = isolate->factory();
   Handle<Map> map = factory->NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
   Handle<JSObject> weakmap_obj = factory->NewJSObjectFromMap(map);
   Handle<JSWeakMap> weakmap(JSWeakMap::cast(*weakmap_obj));
-  // Do not use handles for the hash table, it would make entries strong.
-  Handle<ObjectHashTable> table = ObjectHashTable::New(isolate, 1);
-  weakmap->set_table(*table);
-  weakmap->set_next(Smi::FromInt(0));
+  // Do not leak handles for the hash table, it would make entries strong.
+  {
+    HandleScope scope(isolate);
+    Handle<ObjectHashTable> table = ObjectHashTable::New(isolate, 1);
+    weakmap->set_table(*table);
+  }
   return weakmap;
 }
 
 static void PutIntoWeakMap(Handle<JSWeakMap> weakmap,
                            Handle<JSObject> key,
                            Handle<Object> value) {
   Handle<ObjectHashTable> table = ObjectHashTable::Put(
       Handle<ObjectHashTable>(ObjectHashTable::cast(weakmap->table())),
       Handle<JSObject>(JSObject::cast(*key)),
       value);
@@ skipping 183 matching lines @@
                    Handle<Smi>(Smi::FromInt(i), isolate));
   }
 
   // Force compacting garbage collection. The subsequent collections are used
   // to verify that key references were actually updated.
   CHECK(FLAG_always_compact);
   heap->CollectAllGarbage(Heap::kNoGCFlags);
   heap->CollectAllGarbage(Heap::kNoGCFlags);
   heap->CollectAllGarbage(Heap::kNoGCFlags);
 }