Mac: Add AssertIOAllowed() call to CopyFile()

base/file_util_mac.mm

 // Copyright (c) 2010 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/file_util.h"
 
 #import <Cocoa/Cocoa.h>
 #include <copyfile.h>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/string_util.h"
+#include "base/thread_restrictions.h"
 
 namespace file_util {
 
 bool GetTempDir(FilePath* path) {
   NSString* tmp = NSTemporaryDirectory();
   if (tmp == nil)
     return false;
   *path = FilePath([tmp fileSystemRepresentation]);
   return true;
 }
 
 bool GetShmemTempDir(FilePath* path) {
   return GetTempDir(path);
 }
 
 bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
+  base::ThreadRestrictions::AssertIOAllowed();
   return (copyfile(from_path.value().c_str(),
                    to_path.value().c_str(), NULL, COPYFILE_ALL) == 0);
 }
 
 }  // namespace