Dumping display list levels to rust log

[ibnc]

No description provided.

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/613

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[ibnc]

r=metajack

[ibnc]

Okay, so sort of the idea here was to implement display list dumping similar to flow tree dumping. Flow tree dumping does debug!("{:?}, layout_root.dump()); and I don't really think "{:?}" is avoidable here.

When I use debug!("{}" self.dump()); I get error: failed to find an implementation of trait std::fmt::Default for () I tried the approach of having two separately configured dump functions, but I don't see the display list dumped :/

[metajack]

Fair enough. Keep it as {:?}.