This commit is a limited implementation of the "active formatting
elements" algorithm implemented in HTML5, which preserves certain
formatting elements such as <a> and <b> when exiting or entering nodes.
Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>
Previously, handleEnd was called for any end tag, except ones that were obviously
spurious because there were no parent tags. Now, it is only called for end tags
that are "approved." If an injector operates on the end tag, we automatically
punt. There may be some optimizations that could be made to this procedure,
but for now it's much more consistent.
Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>
