Here's roughly how this works:
- InlineLevelIterator keeps a nesting stack of inline-level nodes with
box model metrics.
- When entering a node with box model metrics, we add them to the
current "leading metrics".
- When exiting a node with box model metrics, we add them to the
current "trailing metrics".
- Pending leading metrics are consumed by the first fragment added
to the line.
- Pending trailing metrics are consumed by the last fragment added
to the line.
Like before, the position of a line box fragment is the top left of its
content box. However, fragments are placed horizontally along the line
with space inserted for padding and border.
InlineNode::paint() now expands the content rect as appropriate when
painting background and borders.
Note that margins and margin collapsing is not yet implemented.
This makes the eyes on ACID2 horizontally centered. :^)
This property represents the CSS content size, so let's reduce ambiguity
by using the spec terminology.
We also bring a bunch of related functions along for the ride.
