Add documentation about the scrolling model
Make sure reftests aren't passing because nothing == nothing

In the test harness, assert that the two images aren't all white.

Fixes #3481
Add support for local font faces. Improves fonts on rust lang and guide.
Create an almost-correct form_owner() for convenience
Add form submission via input element
Add click handler for <input type=submit>
Filter out buttons which aren't the submitter while constructing the dataset
Update wpt expectations
Address review comments
auto merge of #3652 : Manishearth/servo/form-button, r=jdm

Partially fixes #3647
Allow individual layers to render their own background color

Instead of relying on a scene-wide background color, all layers can now
have their own background color.
script: Use atom comparison in more places, especially for attributes.

75% improvement in style recalc for Guardians of the Galaxy.
auto merge of #3675 : glennw/servo/local-fonts, r=pcwalton
try to reset flows which need reflow, since reflow isn't yet idempotent
auto merge of #3623 : pcwalton/servo/use-atoms-2, r=jdm

75% improvement in style recalc for Guardians of the Galaxy.
auto merge of #3634 : mrobinson/servo/scrolling-doc, r=jdm
layout: Introduce support for legacy presentational attributes to selector
matching, and use it for `<input size>` and `<td width>`.

This implements a general framework for legacy presentational attributes
to the DOM and style calculation, so that adding more of them later will
be straightforward.
auto merge of #3622 : pcwalton/servo/html4ever, r=jdm

This implements a general framework for legacy presentational attributes
to the DOM and style calculation, so that adding more of them later will
be straightforward.
auto merge of #3645 : gilles-leblanc/servo/issue-3481, r=kmcallister

In the test harness, assert that the two images aren't all white.

Fixes #3481
layout: Rewrite intrinsic inline-size and automatic table layout to
match L. David Baron's work-in-progress specification.

    http://dbaron.org/css/intrinsic/

Column spans are not yet supported.

This effectively adds support for percentage widths, and it also fixes
many bugs, improving the layout of Google and Wikipedia.