With the changes in this patch stack, it will become more common for frontend
code to receive onLocationChange notifications for subframes, as we will now
correctly report events for oop subframes, and will also deliver notifications
for the first document loaded in subframes in order to update the current remote
URI on CanonicalBrowsingContext.

This change makes more of the callbacks fired by onLocationChange be guarded by
the isTopLevel check, including setting the "URL" crash annotation and updating
the macOS touchbar, which should hopefully both fix existing latent bugs, and
ensure that these issues don't occur with the more frequent onLocationChange
callbacks.

The check in this function was added in bug 82236 to avoid an issue in the
mozilla suite where the UI would update to a subframe's URI. This came up
previously in bug 1206879 when we observed we weren't sending OnLocationChange
events when we were expecting, which was causing issues for pushState location
changes. A workaround was added in that bug to avoid the issue for the specific
case of pushState.

This patch removes the redundant check, and reverts the workaround added in that
bug. Unfortunately, we aren't able to fully remove nsISHEntry::GetIsSubframe, as
it is now used by Browser{Parent,Child}::CanCancelContentJS.

https://hg.mozilla.org/mozilla-central/rev/dfab437ac709
https://hg.mozilla.org/mozilla-central/rev/c7cfaeeb66be