Revert of Allow $TMPDIR to set temporary directory on OS X.

base/files/file_util_mac.mm

Index: base/files/file_util_mac.mm
diff --git a/base/files/file_util_mac.mm b/base/files/file_util_mac.mm
index 5a99aa0e81de2e19110872cc168e53b93555d0c5..e9c6c651593571ca425c1a012db8ec76722938ff 100644
--- a/base/files/file_util_mac.mm
+++ b/base/files/file_util_mac.mm
@@ -4,9 +4,8 @@
 
 #include "base/files/file_util.h"
 
+#include <copyfile.h>
 #import <Foundation/Foundation.h>
-#include <copyfile.h>
-#include <stdlib.h>
 
 #include "base/files/file_path.h"
 #include "base/mac/foundation_util.h"
@@ -24,15 +23,6 @@
 }
 
 bool GetTempDir(base::FilePath* path) {
-  // In order to facilitate hermetic runs on macOS, first check $TMPDIR.
-  // NOTE: $TMPDIR is ALMOST ALWAYS set on macOS (unless the user un-set it).
-  const char* env_tmpdir = getenv("TMPDIR");
-  if (env_tmpdir) {
-    *path = base::FilePath(env_tmpdir);
-    return true;
-  }
-
-  // If we didn't find it, fall back to the native function.
   NSString* tmp = NSTemporaryDirectory();
   if (tmp == nil)
     return false;