[mparch] Use IsInPrimaryMainFrame instead of GetPrimaryMainFrame check

in PermissionRequestManager.

This CL rewrites GetPrimaryMainFrame check to use IsInPrimaryMainFrame
check instead in PermissionRequestManager::AddRequest().

Bug: 1268893
Change-Id: Ie174b0025d501d4810b116e0c2ada42b2bb9ecdb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4022951


Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Kamila Hasanbega <hkamila@chromium.org>
Commit-Queue: Hyowon Kim <hyowon@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1072077}