Change SkMatrix::fixedStepInX to return SkVector (of SkScalar) rather than SkFixed.

All users were immediately converting to SkScalar or SkFixed3232.

This method is not used in Chromium, Android, or Google3.

BUG=skia:4632
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1692013002

Review URL: https://codereview.chromium.org/1692013002
7 files changed