The only remaining callers of RelativeToParent() are in
StackingContextHelper itself, which we can remove now by having the SCH
take a parent SCH and use it instead of RelativeToParent(). This patch
implements this change.
This makes a failing test pass, because of how preserve-3d container
layers work. Specifically, preserve-3d container layers render their
descendants in z-order, not in tree order. If those children were assuming
that their parent had already pushed a stacking context, that assumption
may have been false because the parent might have not yet been rendered
because of z-ordering. By using the StackingContextHelper chain instead
of the layer tree ancestry, we fix the stacking-context-relative coordinates
being used in the descendant subtree of preserve-3d container layers.
MozReview-Commit-ID: HzZvBuAlMdB
This updates more code that was using RelativeToParent() to use the
stacking context helper's ToRelativeWr* functions instead. This get us
closer to breaking the assumption that the WR stacking context order maps
1:1 to the layer tree structure.
MozReview-Commit-ID: HQrbvCgPOW4
This uses the StackingContextHelper and typed helper functions in
WebRenderLayer to simplify WebRenderTextLayer::RenderLayer. It also
removes the implicit assumption in WebRenderTextLayer that the parent
layer pushed a stacking context, which is an assumption we will
probably break in the future.
MozReview-Commit-ID: CARoGVQd56i
This is needed in part 3 to update WebRenderTextLayer::RenderLayer, so
that it no longer assumes the parent container layer has pushed a
stacking context, and instead explicitly uses the StackingContextHelper.
MozReview-Commit-ID: 9twUmDgUipX
This class is a RAII class that can be used to push a stacking context
with properties from a WebRenderLayer. It can also then be used to
convert rects in the layer coordinate system to be relative to the
stacking context, which is what we want for passing to WR.
MozReview-Commit-ID: 1WVrfRYqLqc
