alert dialog box will not change color when switched to Light mode

[btlechowski]

Follow up to brave/brave-core#2352

Steps to Reproduce

1. Clean install
2. Launch Browser
3. Change Brave colors to Dark under brave://settings/appearance
4. Open https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_alert and click Try it (leave alert dialog open)
5. Change Brave colors to Light under brave://settings/appearance
6. Check alert dialog from 4.

Important: Closing the dialog and opening it again will show proper color
Note: Light-Dark theme switch works OK

Actual result:

Alert dialog did not change the color.
Alert dialog remains Dark themed

Expected result:

Alert dialog is Light themed

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	0.66.87 Chromium: 75.0.3770.80 (Official Build) beta (64-bit)
Revision	9a9aa15057b6b2cc0909bdcf638c0b65ecd516f2-refs/branch-heads/3770@{#948}
OS	Windows 7 Service Pack 1 (Build 7601.24465)

cc @brave/legacy_qa @simonhong

[kjozwiak]

Reproduced on macOS 10.14.5 x64 using the following build:

Brave	0.68.60 Chromium: 75.0.3770.90 (Official Build) nightly(64-bit)
Revision	a6dcaf7e3ec6f70a194cc25e8149475c6590e025-refs/branch-heads/3770@{#1003}
OS	Mac OS X

[rebron]

Closing as stale. This looks fixed in 1.40.113 on Windows 11 and macOS.
@btlechowski Can you reopen if still an issue?