Switch Payments LayoutTest to the new Mojo JS bindings

This change rewrites the single Payments API layout test that uses Mojo
mock services to use the new Mojo JS bindings.

Bug: 699569
Change-Id: I6fa74bfb2e926d35ccf3232c87f7a0114592ce9a
Reviewed-on: https://chromium-review.googlesource.com/595246
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Yuzhu Shen <yzshen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491080}
2 files changed