When we removed position: sticky, we introduced a subtle line breaking
bug to pre-wrap that would cause whitespace to accumulate at the
beginning of lines that follow unclean breaks. This patch adds back the
deleted code (cleansed of the position sticky bits).
This complex machinery made sense for Blink, which has hundreds of
developers. In our case, we're just moving around two bools. We can do
that in a much simpler way.
Remove all code relating to shadow trees, insertion points, shadow
boundaries, traversing composed trees, distribution, template
documents, custom elements, registering elements, element registries,
element factories, shadow roots, etc.
Remove the following features from the IDLs and from the binding
generators: CustomElementCallbacks, Reflect*, EventHandler.
Remove the CSS custom pseudo-element concept, since we no longer have
a UA style sheet worth talking about, no longer have shadow trees or
custom elements, no longer use pseudo-elements, and generally
therefore don't use this code at all.
