[heap] Unify the immortal immovable root detection mechanism.

src/unique.h

 // Copyright 2013 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_HYDROGEN_UNIQUE_H_
 #define V8_HYDROGEN_UNIQUE_H_
 
 #include <ostream>  // NOLINT(readability/streams)
 
 #include "src/base/functional.h"
@@ skipping 111 matching lines @@
 
   // TODO(titzer): this is a hack to migrate to Unique<T> incrementally.
   static Unique<T> CreateUninitialized(Handle<T> handle) {
     return Unique<T>(NULL, handle);
   }
 
   static Unique<T> CreateImmovable(Handle<T> handle) {
     return Unique<T>(reinterpret_cast<Address>(*handle), handle);
   }
 
+  T* GetRawAddress() const {
+    DCHECK(IsInitialized());
+    return reinterpret_cast<T*>(raw_address_);
+  }
+
   friend class UniqueSet<T>;  // Uses internal details for speed.
   template <class U>
   friend class Unique;  // For comparing raw_address values.
 
  protected:
   Address raw_address_;
   Handle<T> handle_;
 
   friend class SideEffectsTracker;
 };
@@ skipping 213 matching lines @@
       }
       capacity_ = new_capacity;
       array_ = new_array;
     }
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_UNIQUE_H_