Use hash map to look for objects in the root array when serializing.

src/heap/heap-inl.h

 // Copyright 2012 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_HEAP_HEAP_INL_H_
 #define V8_HEAP_HEAP_INL_H_
 
 #include <cmath>
 
 #include "src/base/platform/platform.h"
@@ skipping 681 matching lines @@
   new_space_strings_.Rewind(position);
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     Verify();
   }
 #endif
 }
 
 
 void Heap::ClearInstanceofCache() {
-  set_instanceof_cache_function(the_hole_value());
+  set_instanceof_cache_function(Smi::FromInt(0));
 }
 
 
 Object* Heap::ToBoolean(bool condition) {
   return condition ? true_value() : false_value();
 }
 
 
 void Heap::CompletelyClearInstanceofCache() {
-  set_instanceof_cache_map(the_hole_value());
-  set_instanceof_cache_function(the_hole_value());
+  set_instanceof_cache_map(Smi::FromInt(0));
+  set_instanceof_cache_function(Smi::FromInt(0));
 }
 
 
 AlwaysAllocateScope::AlwaysAllocateScope(Isolate* isolate)
     : heap_(isolate->heap()), daf_(isolate) {
   // We shouldn't hit any nested scopes, because that requires
   // non-handle code to call handle code. The code still works but
   // performance will degrade, so we want to catch this situation
   // in debug mode.
   DCHECK(heap_->always_allocate_scope_depth_ == 0);
@@ skipping 47 matching lines @@
 
 void VerifySmisVisitor::VisitPointers(Object** start, Object** end) {
   for (Object** current = start; current < end; current++) {
     CHECK((*current)->IsSmi());
   }
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_INL_H_