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
Fix freeze scope extension warning

Fixes #455 (for now)

Also add a comment about how what we're doing here is unsafe (for reasons that
are mostly unrelated to the warning)
auto merge of #656 : kmcallister/servo/dynamic-freeze, r=jdm

Fixes #455 (for now)

Also add a comment about how what we're doing here is unsafe (for reasons that are mostly unrelated to the warning)

r? @tkuehn
auto merge of #657 : tkuehn/servo/master, r=metajack