[Merge M-73][PH][Desktop] Ensure title and origin visibility.

Before this patch, a payment handler with no theme color would result in
white title and origin of the payment handler being displayed on white
dialog background. This caused the title and origin to be invisible.

This patch calculates the resulting background color after applying the
webpage theme color on top of the dialog background, which would never
be transparent and thus the foreground text color is being calculated

After this patch, Chrome shows both the title and the origin of payment
handlers that lack a theme color.


(cherry picked from commit 4678e7afaf51556a7e30470513e7841c7e711eea)

Bug: 926251
Change-Id: I488774c386e9032d6352c6054ccff8b331161e72
Reviewed-on: https://chromium-review.googlesource.com/c/1443628
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#627541}
Reviewed-on: https://chromium-review.googlesource.com/c/1452638
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/branch-heads/3683@{#188}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
1 file changed