Revert of Split parts of //chrome/utility's BUILD.gn into //chrome/utility/safe_browsing/mac.

chrome/utility/safe_browsing/mac/crdmg.cc

Index: chrome/utility/safe_browsing/mac/crdmg.cc
diff --git a/chrome/utility/safe_browsing/mac/crdmg.cc b/chrome/utility/safe_browsing/mac/crdmg.cc
index 8dc0bc9d3cf440aa3348603fa3f090acb6cb056b..18a5ea1535de467b5b70d4971d046641e9ebcc83 100644
--- a/chrome/utility/safe_browsing/mac/crdmg.cc
+++ b/chrome/utility/safe_browsing/mac/crdmg.cc
@@ -24,14 +24,6 @@
 #include "chrome/utility/safe_browsing/mac/hfs.h"
 #include "chrome/utility/safe_browsing/mac/read_stream.h"
 #include "chrome/utility/safe_browsing/mac/udif.h"
-
-// This executable only works on 10.10+, so unconditionally use these functions
-// to make sandboxing easier.
-extern "C" {
-int mkdirat(int, const char *, mode_t);
-int openat(int, const char *, int, ...);
-int unlinkat(int, const char *, int);
-}
 
 namespace {