GitLab

Change:
* Fixed the issue of not being able to launch payment handler twice.
The cause is that when PaymentHandler UI is opened and closed, the
payment handler's PaymentAppProvider was used, instead of the
merchant's.
* Changed PaymentAppProvider to make it one per merchant's WebContents,
not one per payment handler's WebContents.
* Rename WebContents PaymentHandler's codebase to make it better
distinguish between the merchant's and the paymentHandler's.
* Move PaymentAppProvider::SetOpenedWindow() from
service_worker_client_utils into PaymentRequestImpl -->
ServiceWorkerPaymentAppBridge.

Bug: 1131874

Change-Id: I831fec0f3cce0d19abf49d23ccf1e61689afe33a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434101Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Liquan (Max) Gu <maxlg@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811554}