Hide 'user agent stylesheet' CSS in Developer Tools

Description of the issue:
How can this issue be reproduced?

  1. Visit brave.com
  2. Open Developer Tools (Ctrl + Shift + I)
  3. Make sure the Elements tab is active on the left and the Styles tab on the right
  4. Make sure the site’s <body> element is selected in the Elements tab
  5. Scroll down to the bottom of the Style tab and note the ‘user agent stylesheet’ CSS
    E.g.
body {
    display: block;
    margin: 8px;
}

Expected result:
There’s no way to disable the display of ‘user agent stylesheet’ CSS. It’d be nice to be able to hide this and just see the site-specific CSS only.

Brave Version( check About Brave):
Version 1.0.0 Chromium: 78.0.3904.97 (Official Build) (64-bit)