These properties are unused from C++ apart from webidl bindings and the
FakeTreeBoxObject implentations in comm-central are throwing stubs. But
they're used in JS. They are safe to remove from nsITreeBoxObject but we need
to keep an implementation webidl can call into. Properties in this bucket:
selectionRegion, ensureCellIsVisible, scrollToRow, scrollByLines,
scrollByPages, getRowAt, removeImageCacheEntry.
These properties are not used from either JS or C++, and hence can be
removed from both nsITreeBoxObject and TreeBoxObject.webidl. Properties in
this bucket: scrollToCell, scrollToColumn, scrollToHorizontalPosition,
invalidateColumnRange.
There are no consumers of nsITreeBoxObject::SetView, so this fix removes that
setter. There are consumers of GetView, though.
MozReview-Commit-ID: FBEGEFRM9Us
