Incorrect coloring of custom textarea elements (vscode-settings-textInputBackground) with Insiders 1.50.0

[Colengms]

This is based on a user-reported issue with the C/C++ Extension: microsoft/vscode-cpptools#6201

It looks like insiders 1.50 introduced an issue with custom html UI in our extension. We are using the following to color textareas:

color: var(--vscode-settings-textInputForeground);
background: var(--vscode-settings-textInputBackground);

With 1.50.0, this results in a textarea background that matches the page background.

This is the expected behavior, and behavior prior to 1.50.0 :

Version: 1.50.0-insider (user setup)
Commit: f943318
Date: 2020-09-23T06:50:43.482Z
Electron: 9.3.0
Chrome: 83.0.4103.122
Node.js: 12.14.1
V8: 8.3.110.13-electron.0
OS: Windows_NT x64 10.0.19041

[roblourens]

I was able to repro in yesterday's Insiders, but it works for me in today's, please verify. I was working with the settings editor theme colors but got it straightened out yesterday. Sorry!

#106897