Zoom in separate windows

**Description of the issue: Sometimes (did not understand exact criteria) while zooming in or out separate Brave windows (not tabs), zoom changes for all the open windows, not only the one which is active. Sometimes it happens when there are 3 or more windows open, even on the separate monitors.

**Steps to Reproduce (add as many as necessary):

  1. Open 2 windows of Brave
  2. Try to zoom in/out

**Actual Result (gifs and screenshots are welcome!):Gif with the result

**Expected result: Both windows will zoom

**Reproduces how often: N/A

**Operating System and Brave Version(See the About Brave page in the main menu): Microsoft Windows 10 / Brave Version 0.66.101 Chromium: 75.0.3770.142 (Official Build) (64-bit)

Additional Information: