Address review comments:
* Add suggested comments.
* Gecko vbufBackend: move the setting of rerender control properties for parts of tables down to where the rest of the table code is, which means that the resetting of some of them on tabel cells is no longer necessary. The code remains at same scope, and the function never returned or recursed between where the code was to where it is now, so this is safe.
* Gecko vbufBackend: it is no longer necesary to update table counts if a cell is rerendered. If the cell was being rerendered because it was specifically invalidated, then the row/column counts would not have changed, and if the cell was re-rendered due to an ancestor row / row group being invalidated, then the table node would have been rerendered anyway due to requiresParentUpdate being true on the row or row group. However, we still need the tableID from the table to set as an attribute on table cell nodes. Therefore, rename and rewrite updateTableCounts to getTableIDFromCell.
* VBufBackend_t::update: remove the inUpdate check. This issue never actually seems to occur, and no code changes in this pr make it any more likely than it used to be.
