I decided to use the old Netscape broken image link icon (later we may
replace the image asset for something more trendier). The ref test will
expect that a failed load should display the rippy image.
ImageCacheTask users can define if a placeholder image should be loaded
at start up or not. This enables both the new behavior (e.g. always
return an image even for broken urls) as also the previous one.
Additionally, this patch cleans up some miscellaneous formatting issues
and refactors files in `layout/css/` somewhat to eliminate needless
levels of indirection. It also fixes our handling of presentational
hints that only apply if border is nonzero.
matching, and use it for `<input size>` and `<td width>`.
This implements a general framework for legacy presentational attributes
to the DOM and style calculation, so that adding more of them later will
be straightforward.
