Fix Chrome mobile multitouch zoom saccades

[boulabiar]

Since a while, Chrome changed the way it handles how touch events are propagated.
https://tech.slashdot.org/story/17/11/08/1135240/how-chrome-broke-the-web
https://developers.google.com/web/updates/2017/01/scrolling-intervention

This created saccades and a drop in FPS when trying to zoom with two fingers on chrome on mobile.
This fix added an option to the event listener in order to propagate the events directly.

[Mugen87]

I'm confused why this solves the issue for you, see #10373

[boulabiar]

I am also confused, but it solves my problem.

I'm quoting
"
Turned out, Google wasn’t concerned about your websites at all. It was more concerned about its own product performance, Google Chrome Mobile. That’s why on February 1, 2017, they made all top-level event listeners passive by default. They call it “an intervention”.
" from http://tonsky.me/blog/chrome-intervention/

It seems explained here
"
When you add a touch event with a {passive: true} object as the third parameter in your event handler then you are telling the browser that the touchstart listener will not call preventDefault() and the browser can safely perform the scroll without blocking on the listener. For example:
" from https://developers.google.com/web/updates/2017/01/scrolling-intervention

So if I have understood, chrome made some changes that have broken the old behavior.
And in order to be able to preventDefault() you need to make passive false?

[Mugen87]

Closing. A more appropriate fix would be #14013 (comment)