Port external helper app prompting before opening to Fenix
In legacy/trac#26529 (moved) we ported the desktop capability to prompt before opening external apps to mobile. We need to redo that proxy-bypass-protection part for Fenix.
In legacy/trac#26529 (moved) we ported the desktop capability to prompt before opening external apps to mobile. We need to redo that proxy-bypass-protection part for Fenix.