layout: Perform cascading in parallel.

Speeds up the cascade by 3x.
auto merge of #1571 : pcwalton/servo/combine-cascading, r=metajack

Speeds up the cascade by 3x.

r? @metajack
style: Short-circuit the selector matching process if the map is empty.

125% win on selector matching (!)
style: Stop allocating when lowercasing element names for lookup in the
hash.

31% win on selector matching.
Fix white-space property(pre)

If html has empty line, it is not handled currently.
Because pending line is empty in such case, flushing current line doesn't care empty line.
For example, below html has two empty line(line 2 and line 4)
<div>
test1

test2

</div>

To handle empty line, added empty box to pending line.
auto merge of #1574 : pcwalton/servo/cheat-before-after, r=SimonSapin

125% win on selector matching (!)

r? @SimonSapin
auto merge of #1547 : deokjinkim/servo/fix_white_space, r=metajack

If html has empty line, it is not handled currently.
Because pending line is empty in such case, flushing current line doesn't care empty line.
For example, below html has two empty line(line 2 and line 4)
<div>
test1

test2

</div>

To handle empty line, added empty box to pending line.
auto merge of #1566 : pcwalton/servo/fewer-allocations, r=SimonSapin

hash.

31% win on selector matching.

r? @larsbergstrom
Added bound to number of HTTP redirects, and prevented redirect loops.
auto merge of #1562 : wowus/servo/master, r=metajack

Is there a central configuration module which I can query for max_redirects?
Make Node::{remove, insert} take a descriptive enum for suppress_observers instead of a boolean.
auto merge of #1582 : saneyuki/servo/1569, r=Ms2ger

retry: #1581

this will fix #1569
Basic skeleton for DOMException

Spec:
http://dom.spec.whatwg.org/#domexception

This is a subtask for #1542.
layout: Profile layout damage propagation and group "style recalc" (as
WebKit calls it) into one supercategory in the profiler
auto merge of #1587 : pcwalton/servo/profile-damage, r=larsbergstrom

WebKit calls it) into one supercategory in the profiler.

r? @larsbergstrom
layout: Stop adding flows to the leaf set that are obviously never going
to be leaves.

60% improvement in flow tree construction time on the rainbow page.
auto merge of #1589 : pcwalton/servo/stop-removing-flows, r=larsbergstrom

to be leaves.

60% improvement in flow tree construction time on the rainbow page.

r? @larsbergstrom
style: Quicksort rules to avoid allocation of temporary vectors.

17% improvement in selector matching on the rainbow page.
auto merge of #1567 : pcwalton/servo/quicksort-selector-matching, r=larsbergstrom

17% improvement in selector matching on the rainbow page.

r? @larsbergstrom
Implement document.URL & document.documentURI

Specs:
http://dom.spec.whatwg.org/#dom-document-url
http://dom.spec.whatwg.org/#dom-document-documenturi

This is a sub-task for #1428.