Caught by browser test and now blocking all MobileFrontend merges:
Notifications overlay is broken on mobile site.
The error reported in the JS console is:
TypeError: Cannot read property 'bind' of undefined
and it seems to have been introduced by 1575e2bb7a2f686ba4fba71c19bfd70b4c18abc7
Side note: Should MobileFrontend run our browser test suite - this has happened a few times now.