Fix NinePatch decoder when the target is smaller than the source.

If the target is smaller on a given axis than the source then we
just draw a downscaled version of the NinePatch.  If we use the
current path and the source has transparency then areas of the
NinePatch overlap and are blended together resulting in visual
inconsistancy.

bug: 5041053
Change-Id: I0fcc6fb5c214b188a164acf0651aa4ab2f35946d