In the past, the base class implementation of this was used to descend
into subtrees and paint children. That is now taken care of by
StackingContext::paint_descendants() instead, and nothing used this.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
