Decouple root visitors from object visitors.

src/snapshot/serializer-common.cc

 // 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.
 
 #include "src/snapshot/serializer-common.h"
 
 #include "src/external-reference-table.h"
 #include "src/ic/stub-cache.h"
 #include "src/list-inl.h"
 #include "src/objects-inl.h"
@@ skipping 49 matching lines @@
   owns_data_ = true;
   DCHECK(IsAligned(reinterpret_cast<intptr_t>(data_), kPointerAlignment));
 }
 
 // The partial snapshot cache is terminated by undefined. We visit the
 // partial snapshot...
 //  - during deserialization to populate it.
 //  - during normal GC to keep its content alive.
 //  - not during serialization. The partial serializer adds to it explicitly.
 DISABLE_CFI_PERF
-void SerializerDeserializer::Iterate(Isolate* isolate, ObjectVisitor* visitor) {
+void SerializerDeserializer::Iterate(Isolate* isolate, RootVisitor* visitor) {
   List<Object*>* cache = isolate->partial_snapshot_cache();
   for (int i = 0;; ++i) {
     // Extend the array ready to get a value when deserializing.
     if (cache->length() <= i) cache->Add(Smi::kZero);
     // During deserialization, the visitor populates the partial snapshot cache
     // and eventually terminates the cache with undefined.
-    visitor->VisitPointer(&cache->at(i));
+    visitor->VisitRootPointer(Root::kPartialSnapshotCache, &cache->at(i));
     if (cache->at(i)->IsUndefined(isolate)) break;
   }
 }
 
 bool SerializerDeserializer::CanBeDeferred(HeapObject* o) {
   return !o->IsString() && !o->IsScript();
 }
 
 void SerializerDeserializer::RestoreExternalReferenceRedirectors(
     List<AccessorInfo*>* accessor_infos) {
   // Restore wiped accessor infos.
   for (AccessorInfo* info : *accessor_infos) {
     Foreign::cast(info->js_getter())
         ->set_foreign_address(info->redirected_getter());
   }
 }
 
 }  // namespace internal
 }  // namespace v8