- Changes dependency from chrome_helper_app to chrome_helper_app_default
  since there are now mulitple 'chrome_helper_app's.

Chromium changes:

https://chromium.googlesource.com/chromium/src/+/4be2698e4784

commit 4be2698e4784b68198d1062a54942ae232c57c24
Author: Robert Sesek <rsesek@chromium.org>
Date:   Mon Jun 17 17:41:28 2019 +0000

    Create more Mac Helper application bundles.

    In order to enable the hardened runtime, which restricts things such as
    writable-executable memory and loading code signed by a different Team
    ID, special code signing entitlements must be granted to the Helper.
    To keep the capabilities scoped to the process types that require them,
    this CL adds two new variants of the Helper app: one for renderers
    and one for plugins.

    Currently all three Helpers will be code signed in the same way without
    any entitlements, but this will change in the future.

    Tbr: dschuff@chromium.org
    Bug: 850193