Validate external protocols before launching on Windows

Bug: 889459
Change-Id: Id33ca6444bff1e6dd71b6000823cf6fec09746ef
Reviewed-on: https://chromium-review.googlesource.com/c/1256208
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Mustafa Emre Acer <meacer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597611}
DefaultWebClientSetPermission GetDefaultWebClientSetPermission() {
  if (!install_static::SupportsSetAsDefaultBrowser())
    return SET_DEFAULT_NOT_ALLOWED;
  if (ShellUtil::CanMakeChromeDefaultUnattended())
    return SET_DEFAULT_UNATTENDED;
  return SET_DEFAULT_INTERACTIVE;
}

DefaultWebClientSetPermission GetDefaultWebClientSetPermission() {
  if (!install_static::SupportsSetAsDefaultBrowser())
    return SET_DEFAULT_NOT_ALLOWED;
  if (ShellUtil::CanMakeChromeDefaultUnattended())
    return SET_DEFAULT_UNATTENDED;
  return SET_DEFAULT_INTERACTIVE;
}
