[weakrefs] Make WeakCell::Nullify's gc callback a template parameter

Nullify is already defined in an -inl.h, so there is no need for the
extra functionality (and overhead) of std::function.

Bug: v8:8179
Change-Id: I0b149a962409503a9fde150aa1241de74870533e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1972426Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65494}

src/objects/js-weak-refs-inl.h

@@ -172,10 +172,9 @@ Object JSFinalizationGroup::PopClearedCellHoldings(
   return weak_cell->holdings();
 }
 
-void WeakCell::Nullify(
-    Isolate* isolate,
-    std::function<void(HeapObject object, ObjectSlot slot, Object target)>
-        gc_notify_updated_slot) {
+template <typename GCNotifyUpdatedSlotCallback>
+void WeakCell::Nullify(Isolate* isolate,
+                       GCNotifyUpdatedSlotCallback gc_notify_updated_slot) {
   // Remove from the WeakCell from the "active_cells" list of its
   // JSFinalizationGroup and insert it into the "cleared_cells" list. This is
   // only called for WeakCells which haven't been unregistered yet, so they will

src/objects/js-weak-refs.h

@@ -86,10 +86,9 @@ class WeakCell : public TorqueGeneratedWeakCell<WeakCell, HeapObject> {
   // JSFinalizationGroup. Thus we need to tell the GC about the modified slots
   // via the gc_notify_updated_slot function. The normal write barrier is not
   // enough, since it's disabled before GC.
-  inline void Nullify(
-      Isolate* isolate,
-      std::function<void(HeapObject object, ObjectSlot slot, Object target)>
-          gc_notify_updated_slot);
+  template <typename GCNotifyUpdatedSlotCallback>
+  inline void Nullify(Isolate* isolate,
+                      GCNotifyUpdatedSlotCallback gc_notify_updated_slot);
 
   inline void RemoveFromFinalizationGroupCells(Isolate* isolate);