The full constructor for NotificationsAPI::Notification is implemented
along with the getter methods.
It is now possible to call the elements of Notification in JS without
getting undefined but the default values (or the ones passed in
options).
The method `current_wall_time` is added in EnvironmentSettingsObject.
This passes a least a few more tests because of the getter methods
that are created.
https://wpt.live/notifications/constructor-basic.https.htmlhttps://wpt.live/notifications/idlharness.https.any.html
This required a bit of manual manipulation. These tests dynamically
fetch generated IDL files, e.g.:
https://github.com/web-platform-tests/wpt/blob/master/interfaces/streams.idl
Our WPT importer is not able to detect the IDL files that need to be
imported, so dom.idl and streams.idl was copied over manually. Further,
idlharness.js would create URLs of the form "file://interfaces/dom.idl".
So idlharness.js was adapted to create a URL relative to the test file.
