Get scroll performance in VR mode fixed in platform

[cvan]

In working on Gamepad scrolling (issue #55), it was discovered that simply updating scrollTop/scrollLeft (or calling scrollTo) on any element causes the HMD to go black and take 3-6 seconds to update.

This is reproducible with these isolated test cases (drop these into a page with a lot of text):

// Update scroll position every 0.5 seconds.
setInterval(() => {
  document.documentElement.scrollTop += 100;
}, 500);

or

// Update scroll position in 5 seconds.
setTimeout(() => {
  document.documentElement.scrollTop += 500;
}, 5000);

@kearwood is there a Gecko platform bug on file that I could reference? or shall I file one? and with what details (per our discussion last Friday)?

[kearwood]

I think this is a new issue, and may be specific to our VR use case. I'd recommend filing it in bugzilla under "core" product and "layout" component.

[cvan]

will do. thanks!

[cvan]

made a couple isolated test cases (see source) and filed in Bugzilla: bug 1172767.

[jcarpenter]

Team discussion July 13: Kip will first do a quick LOE assessment. Kats is probable person to flag, to start. He and other platform people need our help in resolving, as the development environment is non trivial for setting up. Longer term, landing code in larch and central will make it easier to engage platform devs.

[cvan]

btw, I think we can start listening for mozbrowserasyncscroll for scrolling