[skif] Use Merge() instead of Blend() for drop shadow

Bug: b/323886533
Change-Id: I7f083bb50ca763e132ca9288c2f899d263025d7e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/812996
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed