Eliminate the extra indirection of DList<~Flow>
auto merge of #1626 : kmcallister/servo/flowlist, r=pcwalton

r? @pcwalton

Some points of concern:

* Is this really memory-safe? Is there a way to access a stale `Rawlink` that doesn't exist in the normal `DList` code?
* Is it okay to coerce both `~Flow` and `&Flow` to `(uint, uint)` (or the moral equivalent) and compare them?  Will a given `Flow` always have the same (obj, vtable) regardless of whether it's obtained through `~Flow` or `&Flow`?
Implement document.characterSet

Spec:
http://dom.spec.whatwg.org/#dom-document-characterset

This is a sub-task for #1428.
auto merge of #1604 : brunoabinader/servo/document-characterset, r=Ms2ger

Spec:
http://dom.spec.whatwg.org/#dom-document-characterset

This is a sub-task for #1428.
layout: Lazily create boxes for whitespace, speculating that they won't
be needed.

33% win in flow construction on the rainbow page.
auto merge of #1630 : pcwalton/servo/short-circuit-whitespace, r=larsbergstrom

be needed.

33% win in flow construction on the rainbow page.

r? @larsbergstrom
Implement ProcessingInstruction DOM interface

Spec:
http://dom.spec.whatwg.org/#interface-processinginstruction

Closes #1619.
auto merge of #1620 : brunoabinader/servo/dom-processinginstruction, r=Ms2ger

Spec:
http://dom.spec.whatwg.org/#interface-processinginstruction

Closes #1619.
Implement document.createProcessingInstruction

Spec:
http://dom.spec.whatwg.org/#dom-document-createprocessinginstruction

This is a sub-task for #1428.
auto merge of #1622 : brunoabinader/servo/document-createprocessinginstruction, r=Ms2ger

PR #1620 adds ProcessingInstruction DOM interface.

Spec:
http://dom.spec.whatwg.org/#dom-document-createprocessinginstruction

This is a sub-task for #1428.
Provide AbstractDocument::from_node(node: AbstractNode)

TSIA.
auto merge of #1634 : brunoabinader/servo/document-fromnode, r=jdm

TSIA.

@jdm mentioned to use ```AbstractDocument::from_box``` internally, though.
add case of merge inline info & modify ref test
auto merge of #1577 : ksh8281/servo/inline_add2, r=larsbergstrom

there is a issue when TextRunScanning.
this is for 
```
<span style="background:red;font-size:35px;border: black solid 15px">
        <span style="background:purple; 20px solid">
            <img src="test.jpeg" style="border:blue 30px solid;" />
        </span>
</span>
```
this case. left border of "img" is missing