Assert that we're handed a DOM global in initialize_global.
Implement Location.hash.
Merge pull request #2935 from Ms2ger/location-hash

Implement Location.hash.
Merge pull request #2933 from Ms2ger/initialize_global

Assert that we're handed a DOM global in initialize_global.
Reftest harness explicitly knows whether to run servo in cpu or
gpu mode. This will make it easier to support different expected
behaviours depending on the rendering mode.
Merge pull request #2939 from glennw/reftest-mode

Reftest harness explicitly knows whether to run servo in cpu or gpu mode.