Fix GrRenderTargetContext::drawArc's abandoned Context handling

This was causing a crash in --preAbandonGpuContext mode

Change-Id: Ifbd8eea05402d4db2f06c48f31aa53bce09d0c07
Reviewed-on: https://skia-review.googlesource.com/8310
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed