The patch adds similar to mousemove compression on IPC layer.
https://searchfox.org/mozilla-central/rev/49ed791eec93335abfe6c2880f84c324e73e47e6/dom/ipc/PBrowser.ipdl#764-774
Touch events can't be compressed all the time, because each touch event
may contain changes to several touches.
To disable compression in some cases, another IPC message is sent.
The messages have exactly the same arguments, but by changing the message type,
compression is disabled for that message on IPC layer.
The patch tries to take rather conservative approach by disabling compression
in many cases. Compression is enabled only if the same touches are being changed,
or old touches and some new touch are changed (so the changed touches are a superset of the old touches).
The patch does not do anything with PointerEvent.getCoalescedEvents(). That implementation
would be quite a bit different and riskier for the next coming Fenix release.
Differential Revision: https://phabricator.services.mozilla.com/D63261
--HG--
extra : moz-landing-system : lando
Olli Pettay