Add basic_fetch and a skeleton http_fetch
Add a basic CORS Cache and a CORS Cache trait
Add a task-based CORS Cache
Some docs
Add a canvas create, break script’s dependency on gfx.

The build time on my laptop after touching gfx goes from 1m37s ot 46s.
Remove RenderListener::set_layer_clip_rect

It is currently unused.
Support callback return types in codegen
Merge pull request #3141 from Manishearth/fetch-stuff

Some more Fetch and CORS Cache stuff; r=jdm
Merge pull request #3178 from SimonSapin/canvas-crate

Add a canvas create, break script’s dependency on gfx.
Disable same-origin.html for intermittent failures (fixes #3180).

We don't currently implement the same-origin restriction at all, so there's
little point in running this test.
Merge pull request #3184 from Ms2ger/disable-workers-same-origin-test

Disable same-origin.html for intermittent failures (fixes #3180).; r=jgraham
Merge pull request #3183 from ChrisParis/callback-return

Support callback return types in codegen
Make text decorations be independent display items.

The goal it to avoid having too much layout logic (which gets more complex in vertical text) in gfx code.
Implement sideways text.
Merge pull request #3181 from SimonSapin/sideways-text

Sideways text
Rename AttrList to NamedNodeMap

This fixes issue #3135
Merge pull request #3179 from mrobinson/iframes

Remove RenderListener::set_layer_clip_rect
Merge pull request #3174 from Aaron1011/attrlist-namednodemap

Rename AttrList to NamedNodeMap