Move timer firing implemention into Window #1992
Modify borders ref test to work on OS X

Issue https://github.com/mozilla/servo/issues/2848 has details.
This commit uncomments the borders ref test in basic.list
and modifies the test to work with viewports up to 4096px wide.

Also as a workaround change the html element background to white,
otherwise pixel (0,0) is black (it should be white since the border
at pixel (0, 0) is white. The bug is mostly likely a regression
in rust-layers.
Check for worker scope in responseText setter
Merge pull request #2819 from bjwbell/iframe-layers

Restructure compositor layers to work with iframes.
Merge pull request #2873 from Manishearth/xhr-worker

Check for worker scope in responseText setter; r=Ms2ger
Merge pull request #2874 from bjwbell/borders-ref-test

Modify borders ref test to work on OS X
Revert "Merge pull request #2819 from bjwbell/iframe-layers"

This reverts commit 0200b61f713f2cdddcbc06ccd4cb5de11332899a, reversing
changes made to ca968219025a46e57b5cd770ae7c8ac5919876b1.
Merge pull request #2880 from zwarich/iframes-revert

Revert "Merge pull request #2819 from bjwbell/iframe-layers"
Remove the unused cpu_painting field of CompositorData
Use 'background_color' consistently over 'unrendered_color'
Fix indentation
Simplify CompositorData creation

We already have a layer_properties struct, so we should always use it
instead of passing the information in it out-of-band.
Always create CompositorData with a new layer

Since it makes no sense to create one without the other, the public
interface shouldn't let you do anything else.
Implement Element.matches().
Merge pull request #2876 from saneyuki/match

Implement Element.matches()
Remove unused field before other upcoming changes.
Merge pull request #2883 from glennw/textrun-1

Remove unused field before other upcoming changes; r=Ms2ger
Merge pull request #2850 from ebalint/1992_move_timer_firing_impl

Move timer firing implemention into Window #1992
Make compositing generic over layout_task

This will allow breaking the layout -> compositing dependency
Break the layout -> compositing dependency

This adds a new layout_traits component for the shared trait.
This should allow for faster builds.