Previously the non-native grip was drawn manually with filling
(lots of) pixels to get kind-of 3D effect for grips. This is not
ideal for HiDPI and can also be slow on certain backends.

This commit simplifies grip drawing by just drawng ellipses
(circles actually). This makes it easy to extend the drawing to
support HiDPI scaling and it also looks better and simpler.

Change-Id: I9df192b69f7f920cececf12b40c1f70342e6d485