The left empty space should be removed. Happening on iOS 8.4 (can be emulated on iPhone 5s).
|mediawiki/extensions/MobileFrontend||master||+8 -4||Adjust how position-fixed works in light of new beta|
I actually think ios is doing the right thing here and my bug fix makes sense.
The header of the search is position-fixed so with the drawer open it was correctly being transformed in ios.
I think the bug is thus in in any browser that is not doing this correctly.
https://code.google.com/p/chromium/issues/detail?id=20574 < might be the cause?
Either way I'm confident we are not going to have this issue again, so it's probably not worth any extra investment in time.