Guard resource provider path creation methods against abandoned context

Change-Id: Idb447352d1c39b14137e8bb5af4f3c8fd7378750
Reviewed-on: https://skia-review.googlesource.com/49767
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed