This patch adds a new mechanism that allows InlineFormattingContext to
build line boxes incrementally instead of all-in-one go.
Incremental build will eventually allow much better support for CSS
floating objects.
In #10434 an issue with leading whitespace in new lines after
a <br> element was fixed by checking whether the last fragment
of LineBox is empty.
However, this introduced a regression by which whitespace following
inline elements was swallowed, so `<b>Test</b> 123` would appear
like `Test123`.
By asking specifically if we are handling a forced linebreak
instead of implicity asking for a property that may be shared by
other Node types, we can maintain the correct behavior in regards
to leading whitespace on new lines, as well as trailing whitespace
of inline elements.
There's a subtle difference here. A "block box" in the spec is a
block-level box, while a "block container" is a box whose children are
either all inline-level boxes in an IFC, or all block-level boxes
participating in a BFC.
Notably, an "inline-block" box is a "block container" but not a "block
box" since it is itself inline-level.
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 *
