The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8401134848abbb32f99de0f188f730f706e9ae42

commit 8401134848abbb32f99de0f188f730f706e9ae42
Author: rouslan <rouslan@chromium.org>
Date: Tue Aug 02 23:10:34 2016

Show at most one PaymentRequest UI at a time.

If the webpage calls PaymentRequest.show() while another
PaymentRequest UI is already showing, then reject the second
show() promise.

In addition, this patch performs "OK to create
PaymentRequest" checks inside of the PaymentRequestFactory
instead of the PaymentRequestImpl constructor. That way
PaymentRequestImpl is guaranteed to have a valid state.
This allows many variables in PaymentRequestImpl to become
final.

BUG= 633610 

Review-Url: https://codereview.chromium.org/2192423002
Cr-Commit-Position: refs/heads/master@{#409371}

[modify] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestFactory.java
[modify] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
[modify] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/android/java_sources.gni
[add] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestShowTwiceTest.java
[add] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/test/data/android/payments/payment_request_show_twice_test.html
[add] https://crrev.com/8401134848abbb32f99de0f188f730f706e9ae42/chrome/test/data/android/payments/show_twice.js