Remove TODO about __native_client__ define.

gcc/config/i386/nacl.h

 /* Target definitions for GCC for NativeClient using ELF
    Copyright (C) 1988, 1991, 1995, 2000, 2001, 2002
    Free Software Foundation, Inc.
 
    Derived from sysv4.h written by Ron Guilmette (rfg@netcom.com).
 
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ skipping 186 matching lines @@
    segment descriptor (DS).  That is, instead of
       movl gs:i@NTPOFF, %ecx
    we use
      movl %gs:0, %eax
      movl i@NTPOFF(%eax), %ecx
    There is a slight performance penalty for TLS accesses, but there does not
    seem a way around it.  */
 #undef TARGET_TLS_DIRECT_SEG_REFS_DEFAULT
 #define TARGET_TLS_DIRECT_SEG_REFS_DEFAULT 0
 
-/* TODO(pasko): eliminate the need to define linux-specific macros. Currently
-   Chromium build/build_config.h prevents us from eliminating these defines by
-   not recognizing __native_client__ as a platform.  */
 #define LINUX_TARGET_OS_CPP_BUILTINS()                          \
     do {                                                        \
         builtin_define_std ("unix");                            \
         builtin_assert ("system=unix");                         \
         builtin_assert ("system=posix");                        \
     } while (0)
 
 /* When running in Native Client all inode numbers are identical.
    TODO(pasko): re-enable inode numbers once the relevant bug is fixed:
    http://code.google.com/p/nativeclient/issues/detail?id=1555  */
@@ skipping 72 matching lines @@
 #undef TARGET_USE_BT
 #define TARGET_USE_BT           (ix86_tune_features[X86_TUNE_USE_BT] && !TARGET_NACL)
 
 #undef DBX_REGISTER_NUMBER
 #define DBX_REGISTER_NUMBER(n) \
   (TARGET_64BIT ? dbx64_register_map[n] : svr4_dbx_register_map[n])
 
 #define DWARF2_ADDR_SIZE \
     (TARGET_NACL ? (TARGET_64BIT ? 8 : 4) : \
                    (POINTER_SIZE / BITS_PER_UNIT))