Split distance vector into direction and magnitude components

The vector was split because the vector's users need it split, and we were creating it from the split components in the first place, so it made sense to skip that step.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2223053002

Review-Url: https://codereview.chromium.org/2223053002
3 files changed