[PEPC] Re-check system permissions when the browser window is activated

While the PEPC prompt is showing the kOsSystemSettings screen, it is
expected that the user might change these settings in the OS's settings
UI. This CL re-checks settings when the Chrome Window receives
activation and progresses the PEPC flow if the settings have changed.

Fixed: 383987134
Change-Id: I2857e31ba32fa621ec1cf74246179b30239c1fcd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6182580
Reviewed-by: Thomas Nguyen <tungnh@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1413372}