Make Array::kHeaderSize protected, and only use kHeaderSize of its subclasses...

src/objects.h

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1700 matching lines @@
   // [length]: length of the array.
   inline int length();
   inline void set_length(int value);
 
   // Convert an object to an array index.
   // Returns true if the conversion succeeded.
   static inline bool IndexFromObject(Object* object, uint32_t* index);
 
   // Layout descriptor.
   static const int kLengthOffset = HeapObject::kHeaderSize;
+
+ protected:
+  // No code should use the Array class directly, only its subclasses.
+  // Use the kHeaderSize of the appropriate subclass, which may be aligned.
   static const int kHeaderSize = kLengthOffset + kIntSize;
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kHeaderSize);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Array);
 };
 
 
 // FixedArray describes fixed sized arrays where element
 // type is Object*.
@@ skipping 689 matching lines @@
   // Casting.
   static inline ByteArray* cast(Object* obj);
 
   // Dispatched behavior.
   int ByteArraySize() { return SizeFor(length()); }
 #ifdef DEBUG
   void ByteArrayPrint();
   void ByteArrayVerify();
 #endif
 
+  // ByteArray headers are not quadword aligned.
+  static const int kHeaderSize = Array::kHeaderSize;
+  static const int kAlignedSize = Array::kAlignedSize;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ByteArray);
 };
 
 
 // Code describes objects with on-the-fly generated machine code.
 class Code: public HeapObject {
  public:
   // Opaque data type for encapsulating code flags like kind, inline
   // cache state, and arguments count.
@@ skipping 2299 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_