Make it more explicit when we're converting between SkMatrix and
SkM44 (in either direction).
The IsScaleTranslate helper could have been static in SkCanvas,
but we're probably going to need it when we start pushing SkM44
down to SkDevice.
Change-Id: Ia013c7f59cdbac78b5a04fdcaafb62a0a626cb53
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/284735
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
d8f611dff1