static bool shouldEmitTabBeforeNode(Node* node)
{
    RenderObject* r = node->renderer();
    
    // Table cells are delimited by tabs.
    if (!r || !isTableCell(node))
        return false;
    
    // Want a tab before every cell other than the first one
    RenderTableCell* rc = static_cast<RenderTableCell*>(r);
    RenderTable* t = rc->table();
    return t && (t->cellBefore(rc) || t->cellAbove(rc));
}
CollapsedBorderValue RenderTableCell::collapsedStartBorder() const
{
    RenderTable* table = this->table();
    bool isStartColumn = col() == 0;

    // For the start border, we need to check, in order of precedence:
    // (1) Our start border.
    int start = CSSProperty::resolveDirectionAwareProperty(CSSPropertyWebkitBorderStartColor, table->style()->direction(), table->style()->writingMode());
    int end = CSSProperty::resolveDirectionAwareProperty(CSSPropertyWebkitBorderEndColor, table->style()->direction(), table->style()->writingMode());
    CollapsedBorderValue result(&style()->borderStart(), style()->visitedDependentColor(start), BCELL);

    // (2) The end border of the preceding cell.
    if (RenderTableCell* prevCell = table->cellBefore(this)) {
        CollapsedBorderValue prevCellBorder = CollapsedBorderValue(&prevCell->style()->borderEnd(), prevCell->style()->visitedDependentColor(end), BCELL);
        result = chooseBorder(prevCellBorder, result);
        if (!result.exists())
            return result;
    } else if (isStartColumn) {
        // (3) Our row's start border.
        result = chooseBorder(result, CollapsedBorderValue(&parent()->style()->borderStart(), parent()->style()->visitedDependentColor(start), BROW));
        if (!result.exists())
            return result;
        
        // (4) Our row group's start border.
        result = chooseBorder(result, CollapsedBorderValue(&section()->style()->borderStart(), section()->style()->visitedDependentColor(start), BROWGROUP));
        if (!result.exists())
            return result;
    }
    
    // (5) Our column and column group's start borders.
    bool startColEdge;
    bool endColEdge;
    RenderTableCol* colElt = table->colElement(col(), &startColEdge, &endColEdge);
    if (colElt && startColEdge) {
        result = chooseBorder(result, CollapsedBorderValue(&colElt->style()->borderStart(), colElt->style()->visitedDependentColor(start), BCOL));
        if (!result.exists())
            return result;
        if (colElt->parent()->isTableCol() && !colElt->previousSibling()) {
            result = chooseBorder(result, CollapsedBorderValue(&colElt->parent()->style()->borderStart(), colElt->parent()->style()->visitedDependentColor(start), BCOLGROUP));
            if (!result.exists())
                return result;
        }
    }
    
    // (6) The end border of the preceding column.
    if (!isStartColumn) {
        colElt = table->colElement(col() -1, &startColEdge, &endColEdge);
        if (colElt && endColEdge) {
            CollapsedBorderValue endBorder = CollapsedBorderValue(&colElt->style()->borderEnd(), colElt->style()->visitedDependentColor(end), BCOL);
            result = chooseBorder(endBorder, result);
            if (!result.exists())
                return result;
        }
    } else {
        // (7) The table's start border.
        result = chooseBorder(result, CollapsedBorderValue(&table->style()->borderStart(), table->style()->visitedDependentColor(start), BTABLE));
        if (!result.exists())
            return result;
    }
    
    return result;
}
CollapsedBorderValue RenderTableCell::collapsedRightBorder(bool rtl) const
{
    RenderTable* tableElt = table();
    bool rightmostColumn;
    if (rtl)
        rightmostColumn = col() == 0;
    else {
        int effCol = tableElt->colToEffCol(col() + colSpan() - 1);
        rightmostColumn = effCol == tableElt->numEffCols() - 1;
    }
    
    // For border right, we need to check, in order of precedence:
    // (1) Our right border.
    CollapsedBorderValue result = CollapsedBorderValue(&style()->borderRight(), BCELL);
    
    // (2) The left border of the cell to the right.
    if (!rightmostColumn) {
        RenderTableCell* nextCell = rtl ? tableElt->cellBefore(this) : tableElt->cellAfter(this);
        if (nextCell && nextCell->style()) {
            result = rtl ? compareBorders(CollapsedBorderValue(&nextCell->style()->borderLeft(), BCELL), result) : compareBorders(result, CollapsedBorderValue(&nextCell->style()->borderLeft(), BCELL));
            if (!result.exists())
                return result;
        }
    } else {
        // (3) Our row's right border.
        result = compareBorders(result, CollapsedBorderValue(&parent()->style()->borderRight(), BROW));
        if (!result.exists())
            return result;
        
        // (4) Our row group's right border.
        result = compareBorders(result, CollapsedBorderValue(&section()->style()->borderRight(), BROWGROUP));
        if (!result.exists())
            return result;
    }
    
    // (5) Our column and column group's right borders.
    bool startColEdge;
    bool endColEdge;
    RenderTableCol* colElt = tableElt->colElement(col() + (rtl ? 0 : colSpan() - 1), &startColEdge, &endColEdge);
    if (colElt && (!rtl ? endColEdge : startColEdge)) {
        result = compareBorders(result, CollapsedBorderValue(&colElt->style()->borderRight(), BCOL));
        if (!result.exists())
            return result;
        if (colElt->parent()->isTableCol() && (!rtl ? !colElt->nextSibling() : !colElt->previousSibling())) {
            result = compareBorders(result, CollapsedBorderValue(&colElt->parent()->style()->borderRight(), BCOLGROUP));
            if (!result.exists())
                return result;
        }
    }
    
    // (6) The left border of the column to the right.
    if (!rightmostColumn) {
        colElt = tableElt->colElement(col() + (rtl ? -1 : colSpan()), &startColEdge, &endColEdge);
        if (colElt && (!rtl ? startColEdge : endColEdge)) {
            result = rtl ? compareBorders(CollapsedBorderValue(&colElt->style()->borderLeft(), BCOL), result) : compareBorders(result, CollapsedBorderValue(&colElt->style()->borderLeft(), BCOL));
            if (!result.exists())
                return result;
        }
    } else {
        // (7) The table's right border.
        result = compareBorders(result, CollapsedBorderValue(&tableElt->style()->borderRight(), BTABLE));
        if (!result.exists())
            return result;
    }
    
    return result;
}