1512273 - Use ScrollMetadata::mResolutionUpdated for all main-thread originated resolution changes

Status: NEW

(Core :: Panning and Zooming, enhancement, P3)

Description

[Botond Ballo [:botond]]

Bug 1511137 introduced a mechanism by which the main thread tells APZ when it originates a change to the pres shell resolution, similar to the existing mechanism used for scroll offset updates.

Previously, APZ would use some heuristics to deduce that a pres shell resolution change was originated by the main thread, based on other information in the scroll metadata. Those heuristics are found in this condition [1].

In bug 1511137 I introduced the new mechanism but didn't remove reliance on the existing heuristics. I'd like to do that in this bug, so we only rely on the new mechanism.

[1] https://searchfox.org/mozilla-central/rev/3fdc51e66c9487b39220ad58dcee275fca070ccd/gfx/layers/apz/src/AsyncPanZoomController.cpp#4421

Comment 1

[Botond Ballo [:botond]]

A naive attempt at implementing this is failing some tests:

https://treeherder.mozilla.org/#/jobs?repo=try&tier=1&revision=254a4b69d8a3863d0d3d42879de6d78944d6dd55