impl clipping for GDI raster-handle

BUG=skia:

Change-Id: I66bbcd80853662d982b80e7e504f2b5ccedc055c
Reviewed-on: https://skia-review.googlesource.com/6967
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed