ozone: dri: Use screen location for mouse event dispatch
This works a lot more naturally (no "is window under cursor" checks
during mouse event dispatch) and also will make event coordinates during
capture less awkward (events must be reported relative to the window
origin, but are not bounded by it during capture).
This converts mouse events. Touch events are a followup.
BUG=437035
TEST=unit tests, manual testing on link_freon
Review URL: https://codereview.chromium.org/
762973002
Cr-Commit-Position: refs/heads/master@{#306052}