Avoid redundant weak pointer updates after evacuation.

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 1833 matching lines @@
   set_native_contexts_list(head);
 }
 
 
 void Heap::ProcessAllocationSites(WeakObjectRetainer* retainer) {
   Object* allocation_site_obj =
       VisitWeakList<AllocationSite>(this, allocation_sites_list(), retainer);
   set_allocation_sites_list(allocation_site_obj);
 }
 
+void Heap::ProcessWeakListRoots(WeakObjectRetainer* retainer) {
+  set_native_contexts_list(retainer->RetainAs(native_contexts_list()));
+  set_allocation_sites_list(retainer->RetainAs(allocation_sites_list()));
+}
 
 void Heap::ResetAllAllocationSitesDependentCode(PretenureFlag flag) {
   DisallowHeapAllocation no_allocation_scope;
   Object* cur = allocation_sites_list();
   bool marked = false;
   while (cur->IsAllocationSite()) {
     AllocationSite* casted = AllocationSite::cast(cur);
     if (casted->GetPretenureMode() == flag) {
       casted->ResetPretenureDecision();
       casted->set_deopt_dependent_code(true);
@@ skipping 4480 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8