Use str.char_offset_iter instead of manually calling str.char_range_at.
Remove unused imports in htmlformelement
auto merge of #1031 : luisbg/servo/master, r=kmcallister

HTMLFormElementTypeId, ElementNodeTypeID and Node are not used anymore in htmlformelement.rs

The compiler was giving a warning error about unused imports.
auto merge of #1013 : huonw/servo/text-iter, r=pcwalton

And 3 other minor clean-ups: removing a redundant `if`, a redundant function call, and using `slice_from` where it is possible.
Issue #888 - Node's owner document should never be None.
Address review comment and add fixmes.
auto merge of #1027 : Ms2ger/servo/owner-document, r=jdm

I'm not happy about `is_in_doc`, but that should improve once @jdm lands his document-as-node changes.
Fix infinite-looping reflector() implementation for WindowProxy.
Introduce mutable/immutable variants of reflector() with named lifetimes, and kill unsafe casts.
auto merge of #1032 : bholley/servo/unsafe_reflector_casts, r=jdm

r? @jdm