Remove delay when recalculating viewport height on iOS

It seems that after fixing bug 68832 this does not serve any purpose
anymore. Instead it only delays recalculating the height which results
in a more noticeable jump of the toolbar/overlay header.

Change-Id: Ia9557eb4f544a5e62256873a17d785fe899d4512
Merge "Remove delay when recalculating viewport height on iOS"