Specs: introduce layoutDescendants() to avoid work when a layout
manager is unaffected by its childrens' intrinsic dimensions
Examples: update for layoutDescendants() change
Specs: add "lifetime" to resolver settings so that a transition can
avoid having to dirty every consumer of the property every frame when
it only needs to update the objects that are changing that frame
Specs: expose the parents on AbstractStyleDeclarationList subclasses
Specs: fix documentation around autoreap
Specs: fix definition of setProperty()
Specs: clean up the dimension-related logic of layout managers

Review URL: https://codereview.chromium.org/850593003