Avoid redundant weak pointer updates after evacuation.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index dfd799da36ebc1416ceca04781f4e0ed70734219..5b659736243168cef03d06aeab581f8c156f256a 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1851,6 +1851,10 @@ void Heap::ProcessAllocationSites(WeakObjectRetainer* 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;