Need to set preferred logical widths dirty bits when switching table layout

FixedTableLayout doesn't use the preferred logical widths from its cells to
determine column widths, however it still need to clear the dirty bits to
get notification when style.width changes on the cells.

When a table switches from table-layout:fixed to auto, the preferred logical
widths become meaningful. The dirty value will be used if we cleared the
dirty bit without computing it.

In this patch we do a massive invalidation to the preferred widths on the
cells when table layout has changed.

BUG=b/11113973
R=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/27262002

git-svn-id: svn://svn.chromium.org/blink/trunk@160530 bbb929c8-8fbe-4397-9dbb-9b2b20218538