[NaCl SDK] Re-land "Added support for NaCl IO to use the IRT Extension API."

native_client_sdk/src/libraries/nacl_io/kernel_wrap_bionic.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sys/types.h>  // Include something that will define __BIONIC__.
 
+#include "nacl_io/kernel_wrap.h" // IRT_EXT is turned on in this header.
+
 // The entire file is wrapped in this #if. We do this so this .cc file can be
 // compiled, even on a non-bionic build.
 
-#if defined(__native_client__) && defined(__BIONIC__)
+#if !defined(NACL_IO_IRT_EXT) && defined(__native_client__) && \
+    defined(__BIONIC__)
+
 #include <alloca.h>
 #include <assert.h>
 #include <dirent.h>
 #include <errno.h>
 #include <irt_syscalls.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 
 #include "nacl_io/kernel_intercept.h"
-#include "nacl_io/kernel_wrap.h"
 #include "nacl_io/kernel_wrap_real.h"
 #include "nacl_io/osmman.h"
 
 namespace {
 
 void stat_to_nacl_stat(const struct stat* buf, nacl_abi_stat* nacl_buf) {
   memset(nacl_buf, 0, sizeof(struct nacl_abi_stat));
   nacl_buf->nacl_abi_st_dev = buf->st_dev;
   nacl_buf->nacl_abi_st_ino = buf->st_ino;
   nacl_buf->nacl_abi_st_mode = buf->st_mode;
@@ skipping 487 matching lines @@
 void kernel_wrap_uninit() {
   if (s_wrapped) {
     EXPAND_SYMBOL_LIST_OPERATION(USE_REAL)
     s_wrapped = false;
   }
 }
 
 EXTERN_C_END
 
 #endif  // defined(__native_client__) && defined(__BIONIC__)