Updating FolderIcon drawing to avoid dependency on software layer.

Instead of cliping using clipPath, using PorterDuffXfermode to clear
area outside the bounds. This provides much better support for antialiasing.
Software layer was also being used for drawing shadow. But since the paint
color was set to transparent, no shadow was being drawn in O. Instead drawing
the shadow using radial gradient.

Bug: 35680116
Bug: 35428783
Change-Id: I0431664400628d5d01675fe72fe7ade01b64d611