Translucent gradient rendering bug due to will-change transform

[Jonas Treub]

Overview:

When toggling an element background from a color to a translucent gradient the gradient sometimes gets a black background.
This only appears to happen when will-change transform is enabled for the element.

1) View the example: https://codepen.io/jonastreub/pen/XwbWaR

2) Toggle the element background by clicking it

3) Notice that the gradient has a black background

Expected Results: The gradient to be translucent.

[Radar WebKit Bug Importer]

<rdar://problem/50547664>

[Simon Fraser (smfr)]

Sounds like we're failing to update contentsOpaque.

[Simon Fraser (smfr)]

We currently re-evaluate contentsOpaque in RenderLayerBacking::updateGeometry(), but that doesn't fire for just a background change (repaint triggers an updateConfiguration()). However, contentsOpaque depends on geometry, and updateConfiguration() runs first, so I think we'll have to move it to updateAfterDescendants().

[Simon Fraser (smfr)]

Created attachment 369658 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 369658 [details]
Patch

Clearing flags on attachment: 369658

Committed r245207: <https://trac.webkit.org/changeset/245207>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Simon Fraser (smfr)]

This did not fix bug 197611, so something else is going on there.

[Simon Fraser (smfr)]

*** Bug 197611 has been marked as a duplicate of this bug. ***

[Simon Fraser (smfr)]

*** Bug 196946 has been marked as a duplicate of this bug. ***