Remove #pragma once. Just from base/ for now.

base/os_compat_android.h

 // Copyright (c) 2011 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.
 
 #ifndef BASE_OS_COMPAT_ANDROID_H_
 #define BASE_OS_COMPAT_ANDROID_H_
-#pragma once
 
 #include <fcntl.h>
 #include <sys/types.h>
 #include <utime.h>
 
 // Not implemented in Bionic.
 extern "C" int futimes(int fd, const struct timeval tv[2]);
 
 // The prototype of mkdtemp is missing.
 extern "C" char* mkdtemp(char* path);
 
 // Android has no timegm().
 extern "C" time_t timegm(struct tm* const t);
 
 // The lockf() function is not available on Android; we translate to flock().
 #define F_LOCK LOCK_EX
 #define F_ULOCK LOCK_UN
 inline int lockf(int fd, int cmd, off_t ignored_len) {
   return flock(fd, cmd);
 }
 
 #endif  // BASE_OS_COMPAT_ANDROID_H_