Version: 52.0.2741.0 (Official Build) 19d105a2a1ec66924ff415f27ff170db7a67ba36-refs/heads/master@{#394609} (32/64-bit)
OS: Windows (7,8,8.1,10)

URL: https://chrome.google.com/webstore/detail/material-dark-mkbhd/iiplegjeipnjdpgkeccfccnahofbckad?hl=en

What steps will reproduce the problem?
1) Launch chrome, go to above URL and add the theme (Infobar is seen).
2) Click in omnibox, press Tab key two times (focus moves on Close 'x' button on infobar).
3) Mouse hover on 'Close' button in infobar (button background turns red), press Shift+Tab (do not move mouse) and observe.

On pressing Shift+Tab key, red background behind 'Close' button disappears.

On pressing Shift+Tab key, red background should be seen behind 'Close' button as mouse focus is on 'Close' button.

This is a Regression issue broken in M-51, will soon update other info