Extract code for safely creating SkMasks.

This is in preparation for adding a faster small radii blur.

Change-Id: I8afd4642ebafa63a45031a7a0bd7a720951dc102
Reviewed-on: https://skia-review.googlesource.com/70040
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed