The previous lot of link icons look great on high DPI displays but not
as nice as they could on standard resolution displays. According to
Volker, this is because the SVG paths must appear on integer coordinates
and scale up instead of down. The new assets have been designed with
this consideration in mind.
Also, workaround redundant CSS by adding commenting out the "unvaried"
black SVG background-image selector, selectorWithoutVariant.
Bug: T190549
Bug: T197909
Change-Id: Id341d383018a436401541e82cc75d826688eaaae
Stephen Niedzielski