auto merge of #641 : jdm/servo/htmldoc2, r=jdm

There are several mechanical changes here that make this look more intimidating than it is. DOMStrings are now passed by reference, and Event and Event_ have swapped names. Finally, there are the various places that need to use `document.with_base |doc| { document.foo }` instead of `document.foo`.
auto merge of #645 : jdm/servo/window, r=jdm

This one also looks larger than necessary because GetParentObject needed to be changed to return an Option.
auto merge of #647 : tkuehn/servo/master, r=metajack

This will be necessary for the constellation to properly assign sizes to iframes when a parent layout performs reflow.
auto merge of #654 : tkuehn/servo/master, r=metajack

Fixes #653.
r? @metajack
Merge branch 'master' of git://github.com/mozilla/servo into tkuehn