define OS_BSD on *BSD and replace the ifdefs to use that

base/platform_file_posix.cc

 // 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.
 
 #include "base/platform_file.h"
 
 #include <fcntl.h>
 #include <errno.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
 #include "base/eintr_wrapper.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/utf_string_conversions.h"
 
 #if defined(OS_ANDROID)
 #include "base/os_compat_android.h"
 #endif
 
 namespace base {
 
-#if defined(OS_OPENBSD) || defined(OS_FREEBSD) || \
-    (defined(OS_MACOSX) && \
-     MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_5)
+#if defined(OS_BSD) || (defined(OS_MACOSX) && \
+    MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_5)
 typedef struct stat stat_wrapper_t;
 static int CallFstat(int fd, stat_wrapper_t *sb) {
   base::ThreadRestrictions::AssertIOAllowed();
   return fstat(fd, sb);
 }
 #else
 typedef struct stat64 stat_wrapper_t;
 static int CallFstat(int fd, stat_wrapper_t *sb) {
   base::ThreadRestrictions::AssertIOAllowed();
   return fstat64(fd, sb);
@@ skipping 196 matching lines @@
   info->is_directory = S_ISDIR(file_info.st_mode);
   info->is_symbolic_link = S_ISLNK(file_info.st_mode);
   info->size = file_info.st_size;
   info->last_modified = base::Time::FromTimeT(file_info.st_mtime);
   info->last_accessed = base::Time::FromTimeT(file_info.st_atime);
   info->creation_time = base::Time::FromTimeT(file_info.st_ctime);
   return true;
 }
 
 }  // namespace base