Fix a small leak in FileUtilProxy

BUG=none
TEST=green mem bots

Review URL: http://codereview.chromium.org/7669046

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@97451 0039d316-1c4b-4281-b951-d872f2087c98
  RelayEnsureFileExists(
      scoped_refptr<base::MessageLoopProxy> message_loop_proxy,
      const FilePath& file_path,
      base::FileUtilProxy::EnsureFileExistsCallback* callback)
      : message_loop_proxy_(message_loop_proxy),
        file_path_(file_path),
        callback_(callback),
        created_(false) {
    DCHECK(callback);
  }

  RelayEnsureFileExists(
      scoped_refptr<base::MessageLoopProxy> message_loop_proxy,
      const FilePath& file_path,
      base::FileUtilProxy::EnsureFileExistsCallback* callback)
      : message_loop_proxy_(message_loop_proxy),
        file_path_(file_path),
        callback_(callback),
        created_(false) {
    DCHECK(callback);
  }
