Bug 116926

Consider merging https://chromium.googlesource.com/chromium/blink/+/727ede4b077539383452ab020184714e45a3f5a2 lazyAttach just needs to mark the node as needing a style recalc, there's no reason to mark the node as attached, or mark all the descendants as being attached. We also don't need to mark all descendants as needing a style recalc since Element::recalcStyle is going to transform the StyleChange into a Force when it goes to descendants. Now lazyAttach just marks you as needing a FullStyleChange and the later recalcStyle will mark you as attached. This means that after this patch attached() is equivalent to "ever had style recalc". In a future patch we should rename that flag. A benefit of this patch is that doing appendChild(divWithLotsOfDescendants); now does 2 fewer walks of the descendants because we don't need to mark them all as attached in lazyAttach, and we don't need to run detach() in recalcStyle() when it calls reattach. Another benefit is that Node::attach is no longer n^2 when you append many elements without any whitespace between them because the loop to fix up whitespace can bail out early when it sees !next->attached().