Centralize header/body creation logic.
Another way to repro the vdom bug.
Revert "Another way to repro the vdom bug."

This reverts commit 9d8dd6bb89dede54541d8cd8b1062d98f58ac47d.
A third way to repro the vdom bug.
Revert "A third way to repro the vdom bug."

This reverts commit 961e3a203121f21d5e97c6c202b2fdc51fc202b5.
Extract logic specific to displaying current doc in left sidebar into View.CurrentDoc