remove SetReference from PersistentValueMapBase.

Bug: v8:5828
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I5aabd10a76cd50fefe0ab50ccf239f562cad1522
Reviewed-on: https://chromium-review.googlesource.com/844038Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50718}

include/v8-util.h

@@ -196,16 +196,6 @@ class PersistentValueMapBase {
     return SetReturnValueFromVal(&returnValue, Traits::Get(&impl_, key));
   }
 
-  /**
-   * Call Isolate::SetReference with the given parent and the map value.
-   */
-  void SetReference(const K& key,
-      const Persistent<Object>& parent) {
-    GetIsolate()->SetReference(
-      reinterpret_cast<internal::Object**>(parent.val_),
-      reinterpret_cast<internal::Object**>(FromVal(Traits::Get(&impl_, key))));
-  }
-
   /**
    * Call V8::RegisterExternallyReferencedObject with the map value for given
    * key.