High contrast fix in Settings, devices user agent text input
High contrast fix in Settings, devices user agent text input

Added CSS to update border color in high contrast mode on focus.
https://i.imgur.com/Py1ZizA.gif

Bug:1200980
Change-Id: I3f2d197bef8b9128fe00017938d40a2a0e91469b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2885978
Reviewed-by: Mathias Bynens <17a2cbc4e33156874a9862b0f530521117e66a3d@chromium.org>
Commit-Queue: Chait Pinnamaneni <4a1edc3e01fd90ec0bc124a40864505462f50073@microsoft.com>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend