Example crash: go/crash/7af07fde00000000

If you look at the crash data for all sync IPC renderer hangs, blink.mojom.NotificationServiceProxy.GetPermissionStatus shows up pretty frequently. See: https://crash.corp.google.com/browse?q=product.name%3D%27Chrome%27%20AND%20custom_data.ChromeCrashProto.ptype%3D%27renderer%27%20AND%20custom_data.ChromeCrashProto.magic_signature_1.name%3D%27%5BRenderer%20hang%5D%20mojo%3A%3ASyncHandleRegistry%3A%3AWatchAllHandles%27&ignore_case=false&enable_rewrite=true&omit_field_name=&omit_field_value=&omit_field_opt=%3D#samplereports:5,productversion:1000

Assigning to myself for now until I can triage further.