Decouple root visitors from object visitors.

src/snapshot/partial-serializer.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/partial-serializer.h"
 #include "src/snapshot/startup-serializer.h"
 
 #include "src/objects-inl.h"
 
 namespace v8 {
@@ skipping 23 matching lines @@
     // explicitly when it's loaded.
     if (context->IsNativeContext()) {
       context->set(Context::NEXT_CONTEXT_LINK,
                    isolate_->heap()->undefined_value());
       DCHECK(!context->global_object()->IsUndefined(context->GetIsolate()));
       // Reset math random cache to get fresh random numbers.
       context->set_math_random_index(Smi::kZero);
       context->set_math_random_cache(isolate_->heap()->undefined_value());
     }
   }
-  VisitPointer(o);
+  VisitRootPointer(Root::kPartialSnapshotCache, o);
   SerializeDeferredObjects();
   SerializeEmbedderFields();
   Pad();
 }
 
 void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
                                         WhereToPoint where_to_point, int skip) {
   if (obj->IsMap()) {
     // The code-caches link to context-specific code objects, which
     // the startup and context serializes cannot currently handle.
@@ skipping 92 matching lines @@
       sink_.PutRaw(reinterpret_cast<const byte*>(data.data), data.raw_size,
                    "embedder fields data");
       delete[] data.data;
     }
   }
   sink_.Put(kSynchronize, "Finished with embedder fields data");
 }
 
 }  // namespace internal
 }  // namespace v8