Update compositor clip rect when page size changes. Fixes #2161.
Async XHR GET with basic response header support
auto merge of #2442 : Manishearth/servo/xhr-async, r=jdm

(Note that only `getAllResponseHeaders()` is supported at the moment, I'll be adding the other header methods later.)
Potential fix for #2335.
auto merge of #2411 : glennw/servo/issue-2335, r=pcwalton
auto merge of #2464 : glennw/servo/issue-2161, r=pcwalton
Update Rust.