We were only dumping a PaintableBox' dimensions if its layout node was a
Layout::Box as well, causing us to not dump the dimensions of paintables
for inline nodes in the paintable tree.
In `InlineLevelIterator`, whenever we call `skip_to_next()` and enter a
node with box model metrics, we could potentially accumulate leading and
trailing metrics. This lead to a weird situation where an element with
`display: inline-block` could adopt the leading metrics of an inline
element that follows it, since we perform the call to
`add_extra_box_model_metrics_to_item()` too late.
Move `skip_to_next()` down so it no longer interferes with the `Item`
we're creating.
The test expectation for
`atomic-inline-with-percentage-vertical-align.html` is updated, although
neither the old nor new results are 100% accurate since either box jumps
one pixel to the right.
