[Payments] Restrict just-in-time payment handler to payment method domain and its subdomains

Bug: 853937
Change-Id: I148b3d96950a9d90fa362e580e9593caa6b92a36
Reviewed-on: https://chromium-review.googlesource.com/1132116
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573911}