Reland "Conform to 1D VelocityTracker" (--try 2)

b7977568

Topic for the revert which is being rolled-forward: https://googleplex-android-review.git.corp.google.com/q/topic:revert-19762050-generic_vt-XWGGUQUHYR

Bug: 32830165
Test: android.view.cts.VelocityTrackerTest unaffected; touch fling works

Change-Id: Ifc1e5c3efa06656609ea2021b93706026165af8e