Preserve textarea state when building WikiEditor UI

When we are wrapping the textarea in the Editor UI, the focus state,
cursor position and the scrollposition might get lost. This is
especially annoying on slower machines, where users might have started
using the textarea before the WikiEditor UI was constructed.

Bug: 41911
Change-Id: Ie472c6c88d98f7ba89873a2db73463ef01bd995a
Merge "Preserve textarea state when building WikiEditor UI"