Introduce a base pointer field in FixedTypedArrayBase and teach GC about it

src/objects.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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 4575 matching lines @@
   DECLARE_PRINTER(ExternalFloat64Array)
   DECLARE_VERIFIER(ExternalFloat64Array)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat64Array);
 };
 
 
 class FixedTypedArrayBase: public FixedArrayBase {
  public:
+  // [base_pointer]: For now, points to the FixedTypedArrayBase itself.
+  DECL_ACCESSORS(base_pointer, Object)
+
+  // Dispatched behavior.
+  inline void FixedTypedArrayBaseIterateBody(ObjectVisitor* v);
+
+  template <typename StaticVisitor>
+  inline void FixedTypedArrayBaseIterateBody();
+
   DECLARE_CAST(FixedTypedArrayBase)
 
+  static const int kBasePointerOffset =
+      FixedArrayBase::kHeaderSize + kPointerSize;
+  static const int kHeaderSize = kBasePointerOffset + kPointerSize;
+
   static const int kDataOffset = DOUBLE_POINTER_ALIGN(kHeaderSize);
 
   inline int size();
 
   static inline int TypedArraySize(InstanceType type, int length);
   inline int TypedArraySize(InstanceType type);
 
   // Use with care: returns raw pointer into heap.
   inline void* DataPtr();
 
@@ skipping 6242 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_