Fix truncation of sigma parameter in blur-mask-filtered mask key

This would allow blur-masks alias one another.

Bug: 912595
Bug: 878195
Change-Id: I44e86e893a505cf8abd991975a025cda52011db6
Reviewed-on: https://skia-review.googlesource.com/c/181902
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
1 file changed