RenderTableCell m_row and m_column should not be signed values

RenderTableCell m_row and m_column should not be signed values
https://bugs.webkit.org/show_bug.cgi?id=70369

Reviewed by Darin Adler.

No new tests, refactoring only.

The gist of the change is to update row / column handling in the table's
rendering code to use unsigned values. Not all the code is switched over
to unsigned but this is a good start.

Using unsigned makes a lot more sense that allowing some negative indexes
to creep in the algorithms. Also it enables us to "free" the unused signed
bit on the 2 RenderTableCell fields that can be used to pack 2 bits in a
follow-up patch.

* accessibility/AccessibilityTable.cpp:
(WebCore::AccessibilityTable::cellForColumnAndRow):
Removed 2 casts to int as the left side now computes to an unsigned too.
Added some ASSERT to make sure we don't get negative values (colSpan / rowSpan
are always >= 1 by definition but better to be safe).

* accessibility/AccessibilityTableColumn.cpp:
(WebCore::AccessibilityTableColumn::headerObjectForSection):
* accessibility/AccessibilityTableColumn.h:
Switched m_columnIndex to unsigned to remove any signed / unsigned comparisons.

* rendering/RenderTable.cpp:
(WebCore::RenderTable::splitColumn):
(WebCore::RenderTable::calcBorderEnd):
(WebCore::RenderTable::cellAbove):
(WebCore::RenderTable::cellBelow):
(WebCore::RenderTable::cellBefore):
(WebCore::RenderTable::cellAfter):
Mostly mechanical changes to avoid signed / unsigned comparisons or casts.

* rendering/RenderTable.h:
(WebCore::RenderTable::numEffCols):
(WebCore::RenderTable::colToEffCol):
Updated a couple of functions to use an unsigned.

* rendering/RenderTableCell.cpp:
(WebCore::RenderTableCell::RenderTableCell):
* rendering/RenderTableCell.h:
(WebCore::RenderTableCell::col):
(WebCore::RenderTableCell::setCol):
(WebCore::RenderTableCell::row):
(WebCore::RenderTableCell::setRow):
Updated after switching the fields to unsigned. Also added 2 constants
to cover the not-initialized-yet value for row and column indexes.
Note: we don't enforce that you can't reach those indexes but neither
did the previous code!

* rendering/RenderTableSection.cpp:
(WebCore::RenderTableSection::RenderTableSection):
(WebCore::RenderTableSection::addChild):
(WebCore::RenderTableSection::ensureRows):
(WebCore::RenderTableSection::setCellLogicalWidths):
(WebCore::RenderTableSection::calcRowLogicalHeight):
(WebCore::RenderTableSection::layoutRows):
(WebCore::RenderTableSection::calcOuterBorderStart):
(WebCore::RenderTableSection::calcOuterBorderEnd):
(WebCore::RenderTableSection::recalcCells):
(WebCore::RenderTableSection::clearGrid):
(WebCore::RenderTableSection::numColumns):
(WebCore::RenderTableSection::appendColumn):
(WebCore::RenderTableSection::splitColumn):
Lots of mechanical: signed -> unsigned changes. However we had
to change the logic a bit as it assumed that m_cRow started at
-1 and increased from there. The new meaning of m_cRow is the
number of rows seen and m_cRow - 1 is where to insert your new
cells.

(WebCore::RenderTableSection::addCell):
Checked the callers and all increase m_cRow before calling the function.
Added an ASSERT to catch up wrong usage in the future.

* rendering/RenderTableSection.h:
(WebCore::RenderTableSection::numRows): Switched to unsigned.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@98676 268f45cc-cd09-0410-ab3c-d52691b4dbfc