optimize for diff matrix types

Bug: skia:
Change-Id: I671e07c5bbb9e4ced92303c9959143324f7a6bdc
Reviewed-on: https://skia-review.googlesource.com/21523
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Herb Derby <herb@google.com>
5 files changed