[Payment Request] Show PaymentDetails.error.

Before this patch, Chrome would not show the merchant's shipping address
validation error message if the merchant also provided some shipping
options.

This patch shows the error message if the merchant sets it or if the
merchant clears the shipping options in an update.

After this patch, Chrome shows the merchant's shipping address
validation error message even if the merchant provided some shipping
options.

As before, if the merchant clears shipping options in an update without
providing an error message, Chrome displays a default error message.
This behavior has not changed.

Bug: 934902
Change-Id: Idfeef5963fd1c9e12d7cdfe1ec9afedd51563a8d
Reviewed-on: https://chromium-review.googlesource.com/c/1482720
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636488}
8 files changed