Adaptively use temp dir instead of /dev/shm for executable shmem file on Linux

base/file_util_mac.mm

Index: base/file_util_mac.mm
diff --git a/base/file_util_mac.mm b/base/file_util_mac.mm
index 95d4f25722a9d9859ff4dd169bf23bef6a248db1..bb4975d4555b69a596012c2c646a2f099ef7dd41 100644
--- a/base/file_util_mac.mm
+++ b/base/file_util_mac.mm
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -22,7 +22,7 @@ bool GetTempDir(FilePath* path) {
   return true;
 }
 
-bool GetShmemTempDir(FilePath* path) {
+bool GetShmemTempDir(FilePath* path, bool executable) {
   return GetTempDir(path);
 }