This removes CefBrowserSettings.universal_access_from_file_urls and
CefBrowserSettings.file_access_from_file_urls. Due to NetworkService
requirements these values must now be configured globally via command-line
flags ("allow-universal-access-from-files" and "allow-file-access-from-files"
respectively).
Also remove the kAllowFileAccessFromFileUrls switch in CEF which duplicates
the existing kAllowFileAccessFromFiles switch in Chromium (see issue #1785).