Move AnimateInkDrop into InkDropEventHandler

This moves event caching and OS-specific code from InkDropHostView which
needs to be shared with installable InkDrops.

Bug: chromium:939419
Change-Id: Ib50ec1dfc562c35acd7eb2a5df77ad35aee2d84b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531298
Reviewed-by: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642934}
4 files changed