I ran all the JavaScript-based web platform tests on Safari and Chrome, using an iPhone 7 simulator running iOS 11 beta 4.

I used a locally-built Chrome at r495947, and web platform tests at revision https://github.com/w3c/web-platform-tests/commit/a574530634a7e3f1c4e4f0385ec8e32620468def.

All tests/subtests that behaved differently on Chrome vs Safari are listed here: https://docs.google.com/spreadsheets/d/1_aciGYA9DNsp1eu4Viest2z6ZZLpGXvBeRfA9Bg3kio

I'll file sub-bugs for individual tests (or groups of related tests).