Decouple root visitors from object visitors.

src/snapshot/deserializer.h

 // Copyright 2016 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.
 
 #ifndef V8_SNAPSHOT_DESERIALIZER_H_
 #define V8_SNAPSHOT_DESERIALIZER_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 #include "src/snapshot/serializer-common.h"
@@ skipping 45 matching lines @@
   // Deserialize an object graph. Fail gracefully.
   MaybeHandle<HeapObject> DeserializeObject(Isolate* isolate);
 
   // Add an object to back an attached reference. The order to add objects must
   // mirror the order they are added in the serializer.
   void AddAttachedObject(Handle<HeapObject> attached_object) {
     attached_objects_.Add(attached_object);
   }
 
  private:
-  void VisitPointers(Object** start, Object** end) override;
+  void VisitRootPointers(Root root, Object** start, Object** end) override;
 
   void Synchronize(VisitorSynchronization::SyncTag tag) override;
 
-  void VisitRuntimeEntry(RelocInfo* rinfo) override { UNREACHABLE(); }
-
   void Initialize(Isolate* isolate);
 
   bool deserializing_user_code() { return deserializing_user_code_; }
 
   void DecodeReservation(Vector<const SerializedData::Reservation> res);
 
   bool ReserveSpace();
 
   void UnalignedCopy(Object** dest, Object** src) {
     memcpy(dest, src, sizeof(*src));
@@ skipping 67 matching lines @@
 
   AllocationAlignment next_alignment_;
 
   DISALLOW_COPY_AND_ASSIGN(Deserializer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_DESERIALIZER_H_