Initialize the swizzler if there is a subset

Bug: b/64077740

Change-Id: Ic6bef3f63bcda24fc3d88ce0cdcf1216441faa40
Reviewed-on: https://skia-review.googlesource.com/37680
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed