Update web-platform-tests expectations.
Remove an unnecessary string copy in the Text constructor.
Merge pull request #2838 from Ms2ger/text-clone

Remove an unnecessary string copy in the Text constructor.
Rename variables that refer to global objects.

This clarifies whether those variables will point to a Window object or an
arbitrary global object.

Note in particular that all IDL Constructors will accept an arbitrary global
object.
Simplify the implementation of cx_for_dom_reflector.
Put some 'use' statements in alphabetical order.
Make some DOM fields private.

Relevant to #2242.
Remove some Cells for immutable members.
Introduce abstractions for global scopes.

Part of #2811.
Merge pull request #2825 from Ms2ger/wpt-expectations

Update web-platform-tests expectations.
Support FormData outside Window scopes.
Add newlines in global.rs.
Merge pull request #2839 from Ms2ger/globals

Introduce abstractions for global scopes; r=Manishearth,larsberg
Changes to support latest rust-layers

Now tiles are stored in TileGrid and layer methods are simple instance
methods.
Respond to review comments
Merge pull request #2843 from mrobinson/tilegrid

Changes to support latest rust-layers
Temporarily disable the 'borders' test

This test has been failing locally on OS X for me for quite some time,
although since #2843 this started affecting the Travis builders as well.
Getting to the root of this problem is tracked by #2848.
Merge pull request #2849 from zwarich/disable-borders-test

Temporarily disable the 'borders' test