Hi Rui, we've added 14dp border on top and bottom of the header in above screenshot to center it (used have 14dp on top and 8dp on bottom).

Does it look good to you?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/28df35396ca1d1013c7767fb44a4fcc65e751b7f

commit 28df35396ca1d1013c7767fb44a4fcc65e751b7f
Author: gogerald <gogerald@google.com>
Date: Tue May 08 15:07:25 2018

[Payments] Center payment request dialog header

Bug:  840803 
Change-Id: I3cf9698c58f8c7e885b16123c05e4a15f8ba53c8
Reviewed-on: https://chromium-review.googlesource.com/1049952
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556800}
[modify] https://crrev.com/28df35396ca1d1013c7767fb44a4fcc65e751b7f/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.cc
[modify] https://crrev.com/28df35396ca1d1013c7767fb44a4fcc65e751b7f/chrome/browser/ui/views/payments/payment_request_views_util.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/672ae4ef55b034ce148a0c6d8ca3b2261d60fea4

commit 672ae4ef55b034ce148a0c6d8ca3b2261d60fea4
Author: gogerald <gogerald@google.com>
Date: Fri May 11 12:35:08 2018

[Payments] Update payment handler opened window

1, Added a progress bar to indicate page loading progress.
   The progress bar is hidden when progress is 1.0.
2, Moved payment handler icon from left to right.
3, Replaced the info icon with the gear icon.

Bug:  840803 
Change-Id: I0386d268b54585c54836229ca7fece76fea5a4fd
Reviewed-on: https://chromium-review.googlesource.com/1053791
Reviewed-by: anthonyvd <anthonyvd@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557850}
[modify] https://crrev.com/672ae4ef55b034ce148a0c6d8ca3b2261d60fea4/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.cc
[modify] https://crrev.com/672ae4ef55b034ce148a0c6d8ca3b2261d60fea4/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.h
[modify] https://crrev.com/672ae4ef55b034ce148a0c6d8ca3b2261d60fea4/chrome/browser/ui/views/payments/payment_request_sheet_controller.cc

Tried to test the issue with the URL: https://rsolomakhin.github.io/, shown error message: "NotSupportedError: The payment methods "https://emerald-eon.appspot.com/bobpay", "interledger" are not supported", find attached screencast for reference.

@gogerald: Could you please provide sample test file/URL that reproduces the issue which helps us in verifying and confirming the fix.

Thanks!

Deleted: 840803.ogv 1.1 MB

	840803.ogv 1.1 MB View Download

Have you turned on '#service-worker-payment-apps'?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/163a0bdc8bf394c040d935661f85f34ae0000a22

commit 163a0bdc8bf394c040d935661f85f34ae0000a22
Author: gogerald <gogerald@google.com>
Date: Wed May 16 00:25:24 2018

[Payment] Update opened payment handler window header.

This CL:
1, Added a static separator between header and web contents
2, Removed site settings' icon

Bug:  840803 
Change-Id: I0a2cfdf1f5d6d128054faec5edde0ba3d390f28e
Reviewed-on: https://chromium-review.googlesource.com/1057409
Reviewed-by: anthonyvd <anthonyvd@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558896}
[modify] https://crrev.com/163a0bdc8bf394c040d935661f85f34ae0000a22/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.cc
[modify] https://crrev.com/163a0bdc8bf394c040d935661f85f34ae0000a22/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.h
[modify] https://crrev.com/163a0bdc8bf394c040d935661f85f34ae0000a22/chrome/browser/ui/views/payments/payment_request_dialog_view_ids.h
[modify] https://crrev.com/163a0bdc8bf394c040d935661f85f34ae0000a22/chrome/browser/ui/views/payments/payment_request_sheet_controller.cc
[modify] https://crrev.com/163a0bdc8bf394c040d935661f85f34ae0000a22/chrome/browser/ui/views/payments/payment_request_sheet_controller.h

Able to reproduce the issue on Mac 10.13.3 using chrome version without fix.

Verified the fix on Mac 10.13.3, Win-10 and Ubuntu 17.10 using Chrome version #68.0.3432.0 as per the comment # and #9.
Attaching screen cast and screen shot for reference.
Observed that a static separator is added between header and web contents, site settings icon is removed, a progress bar has been added to indicate page loading progress and payment handler icon is moved from left to right.
Hence, the fix is working as expected. 
Adding the verified labels.

Thanks...!!

Deleted: 840803.mp4 869 KB

	840803.mp4 869 KB View Download

Deleted: 840803@bobpay.png 104 KB

	840803@bobpay.png 104 KB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5ea927a58d8fb8f2d35eddfb94e9da4eb3ea6914

commit 5ea927a58d8fb8f2d35eddfb94e9da4eb3ea6914
Author: gogerald <gogerald@google.com>
Date: Wed May 16 15:43:45 2018

[Payment] Update progress bar color in opened payment handler window

Bug:  840803 
Change-Id: I73adf2f8279ba491200cd027e29a493b45d6590d
Reviewed-on: https://chromium-review.googlesource.com/1060602
Commit-Queue: Mathieu Perreault <mathp@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559118}
[modify] https://crrev.com/5ea927a58d8fb8f2d35eddfb94e9da4eb3ea6914/chrome/browser/ui/views/payments/payment_handler_web_flow_view_controller.cc