[Merge M-56] Enable canMakePayment() for web payments.

Intent to implement and ship:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/IoIxRpn6l9g/ux1C1Cj7AQAJ

Spec:
https://w3c.github.io/browser-payment-api/#canmakepayment-method

Added in:
https://github.com/w3c/browser-payment-api/pull/380

BUG=664619

Review-Url: https://codereview.chromium.org/2579793003
Cr-Commit-Position: refs/heads/master@{#438995}
(cherry picked from commit 641294913f8d3550ccfe15d5ab1285e180513ab4)

Review-Url: https://codereview.chromium.org/2581683006 .
Cr-Commit-Position: refs/branch-heads/2924@{#526}
Cr-Branched-From: 3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
7 files changed