Replace some deprecated usages of readdir_r with readdir

base/files/file_enumerator_posix.cc

Index: base/files/file_enumerator_posix.cc
diff --git a/base/files/file_enumerator_posix.cc b/base/files/file_enumerator_posix.cc
index fb4010aadcad566f304a899344f1cb892b666081..33a9d9f442ef60d7f61d76b5da010b3944c23416 100644
--- a/base/files/file_enumerator_posix.cc
+++ b/base/files/file_enumerator_posix.cc
@@ -131,9 +131,7 @@ bool FileEnumerator::ReadDirectory(std::vector<FileInfo>* entries,
          additional space for pathname may be needed
 #endif
 
-  struct dirent dent_buf;
-  struct dirent* dent;
-  while (readdir_r(dir, &dent_buf, &dent) == 0 && dent) {
+  for (struct dirent* dent = readdir(dir); dent; dent = readdir(dir)) {
     FileInfo info;
     info.filename_ = FilePath(dent->d_name);