[runtime] Move heap-object type check helpers to HeapObject with wrapper on Object

src/heap/mark-compact-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_MARK_COMPACT_INL_H_
 #define V8_HEAP_MARK_COMPACT_INL_H_
 
 #include "src/heap/mark-compact.h"
 #include "src/heap/slots-buffer.h"
 #include "src/isolate.h"
@@ skipping 76 matching lines @@
   if (target_page->IsEvacuationCandidate() &&
       !ShouldSkipEvacuationSlotRecording(object)) {
     CHECK(SlotsBuffer::AddTo(slots_buffer_allocator_,
                              target_page->slots_buffer_address(), slot,
                              SlotsBuffer::IGNORE_OVERFLOW));
   }
 }
 
 
 void CodeFlusher::AddCandidate(SharedFunctionInfo* shared_info) {
-  if (GetNextCandidate(shared_info) == NULL) {
+  if (GetNextCandidate(shared_info) == nullptr) {
     SetNextCandidate(shared_info, shared_function_info_candidates_head_);
     shared_function_info_candidates_head_ = shared_info;
   }
 }
 
 
 void CodeFlusher::AddCandidate(JSFunction* function) {
   DCHECK(function->code() == function->shared()->code());
-  if (GetNextCandidate(function)->IsUndefined()) {
+  if (function->next_function_link()->IsUndefined()) {
     SetNextCandidate(function, jsfunction_candidates_head_);
     jsfunction_candidates_head_ = function;
   }
 }
 
 
 JSFunction** CodeFlusher::GetNextCandidateSlot(JSFunction* candidate) {
   return reinterpret_cast<JSFunction**>(
       HeapObject::RawField(candidate, JSFunction::kNextFunctionLinkOffset));
 }
@@ skipping 80 matching lines @@
     }
     if (object != nullptr) return object;
   }
   return nullptr;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_INL_H_