Optimize clearing of map transitions.

src/heap/heap.cc

 // 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.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 2468 matching lines @@
 AllocationResult Heap::AllocateWeakCell(HeapObject* value) {
   int size = WeakCell::kSize;
   STATIC_ASSERT(WeakCell::kSize <= Page::kMaxRegularHeapObjectSize);
   HeapObject* result = nullptr;
   {
     AllocationResult allocation = AllocateRaw(size, OLD_SPACE);
     if (!allocation.To(&result)) return allocation;
   }
   result->set_map_no_write_barrier(weak_cell_map());
   WeakCell::cast(result)->initialize(value);
-  WeakCell::cast(result)->clear_next(this);
+  WeakCell::cast(result)->clear_next(the_hole_value());
   return result;
 }
 
 
 AllocationResult Heap::AllocateTransitionArray(int capacity) {
   DCHECK(capacity > 0);
   HeapObject* raw_array = nullptr;
   {
     AllocationResult allocation = AllocateRawFixedArray(capacity, TENURED);
     if (!allocation.To(&raw_array)) return allocation;
@@ skipping 3617 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8