vp8: Remove isolated skin & non skin blocks.
vp8: Remove isolated skin & non skin blocks.

Neutral on RTC metrics and speed on Pixel.

Change-Id: I26b907483fe133e6e4c1009d147631f0d0e0f2fb

ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx