Make x64 to use the RecordWrite stub. This is a step towards getting

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 1376 matching lines @@
   inline int available_space() const {
     return static_cast<int>(reloc_info_writer.pos() - pc_);
   }
 
   static bool IsNop(Address addr) { return *addr == 0x90; }
 
   // Avoid overflows for displacements etc.
   static const int kMaximalBufferSize = 512*MB;
   static const int kMinimalBufferSize = 4*KB;
 
+  byte byte_at(int pos)  { return buffer_[pos]; }
+  void set_byte_at(int pos, byte value) { buffer_[pos] = value; }
+
  protected:
   bool emit_debug_code() const { return emit_debug_code_; }
 
  private:
   byte* addr_at(int pos)  { return buffer_ + pos; }
-  byte byte_at(int pos)  { return buffer_[pos]; }
-  void set_byte_at(int pos, byte value) { buffer_[pos] = value; }
   uint32_t long_at(int pos)  {
     return *reinterpret_cast<uint32_t*>(addr_at(pos));
   }
   void long_at_put(int pos, uint32_t x)  {
     *reinterpret_cast<uint32_t*>(addr_at(pos)) = x;
   }
 
   // code emission
   void GrowBuffer();
 
@@ skipping 216 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_