[css-tables] Speculative workaround for crash

RecalcVisualOverflow might be trying to read a cell that's been removed
from the tree.

I've not been able to get this to repro on android or linux.

Bug: 956625
Change-Id: I1353bd537245fc458e9eeec48bd8861b70364cf7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617559Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661121}

third_party/blink/renderer/core/layout/layout_table_section.cc

@@ -1742,6 +1742,7 @@ unsigned LayoutTableSection::NumEffectiveColumns() const {
 LayoutTableCell* LayoutTableSection::OriginatingCellAt(
     unsigned row,
     unsigned effective_column) {
+  SECURITY_CHECK(!needs_cell_recalc_);
   if (effective_column >= NumCols(row))
     return nullptr;
   auto& grid_cell = GridCellAt(row, effective_column);