GitLab

Add ScrollData and EventMomentumPhase mojo struct, enum, and traits.
Remove lossy ScrollEvent conversion code from PlatformDisplayDefault.
Generalize some EventDispatcher code to support non-pointer events.
Add a basic StructTraitsTest.ScrollEvent unit test.

Bug: 602859, b/73663094
Test: onemilescroll.com, Arc++ scrolls/flings with --enable-features=Mus
Change-Id: Ib6ba95fdd79aa67d5ad1b6b7c4ff9f4b38b3e45b
Reviewed-on: https://chromium-review.googlesource.com/940607Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540367}