Reenable the second wpt chunk.
layout: Remove `layout/extra.rs`.

Also, rename a few methods in layout that arguably had confusing names.
Dump initial prototype of devtools server into the build. Expect lies if you try to use it for anything real.
Enable executing JS snippets in the context of the main Servo window and viewing the responses from the Firefox remote console.
Split devtools implementation into sensible modules.
Avoid selecting on the devtools port if no devtools server exists.
Implement wire protocol support for DOM inspector.
Enable real DOM inspector support.
Retrieve some basic layout properties for nodes to make the box model somewhat useful.
Implement TreeWalker
Fix padding on tables. This fixes the TOC on wikipedia pages.

Ref: #2554
Merge pull request #3421 from glennw/table-padding

Fix padding on tables. This fixes the TOC on wikipedia pages.
Fix img with display: block. Fixes text/image overflow on wikipedia.

Ref: #2554
Merge pull request #3419 from glennw/img-block

Fix img with display: block. Fixes text/image overflow on wikipedia.
Merge pull request #3172 from jdm/devtools

Dump initial prototype of devtools server into the build. Expect lies if...
Merge pull request #3393 from jdm/wptchunk2

Reenable the second wpt chunk.
Merge pull request #3401 from pcwalton/refactor-layout

layout: Remove `layout/extra.rs`.
Merge pull request #3253 from ChrisParis/TreeWalker

Implement TreeWalker
Handle generated content with `display: block` correctly during flow
construction.

The iteration was incorrect here. Although it accidentally worked
before, it will cause problems when we have incremental style
recalculation.

The `after_block_iteration` reftest will become interesting once we have
incremental style recalc.
Merge pull request #3399 from pcwalton/fix-generated-content-iteration

Handle generated content with `display: block` correctly during flow