Peek is used to determine if the current chunk is
the last and if so, add trailing box metrics.
For this to work correctly, it must be done only
after calling next(), otherwise peek gives us the
current chunk.
Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
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.
