diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index b67ab0bd7166..7f9112994d6d 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -3168,7 +3168,7 @@ def __init__(self, errorResult, arguments, argsPre, returnType,
 
         if isFallible:
             if static:
-                glob = "&global"
+                glob = "global.upcast::<GlobalScope>()"
             else:
                 glob = "&this.global()"
 
@@ -5245,12 +5245,18 @@ def __init__(self, descriptor, constructor=None):
             assert constructor
         CGAbstractExternMethod.__init__(self, descriptor, name, 'bool', args)
         self.constructor = constructor
+        self.exposureSet = descriptor.interface.exposureSet
 
     def definition_body(self):
-        preamble = CGGeneric("""\
-let global = GlobalScope::from_object(JS_CALLEE(cx, vp).to_object());
-let args = CallArgs::from_vp(vp, argc);
-""")
+        preamble = """let global = GlobalScope::from_object(JS_CALLEE(cx, vp).to_object());\n"""
+        if len(self.exposureSet) == 1:
+            globalName = list(self.exposureSet)[0]
+            downcast = """let global = global.downcast::<dom::{}::{}>().unwrap();\n"""
+            downcast = downcast.format(globalName.lower(),
+                                       MakeNativeName(globalName))
+            preamble += downcast
+        preamble += """let args = CallArgs::from_vp(vp, argc);\n"""
+        preamble = CGGeneric(preamble)
         name = self.constructor.identifier.name
         nativeName = MakeNativeName(self.descriptor.binaryNameFor(name))
         callGenerator = CGMethodCall(["&global"], nativeName, True,
@@ -5581,6 +5587,7 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         'dom::bindings::error::throw_dom_exception',
         'dom::bindings::guard::Condition',
         'dom::bindings::guard::Guard',
+        'dom::bindings::inheritance::Castable',
         'dom::bindings::proxyhandler',
         'dom::bindings::proxyhandler::ensure_expando_object',
         'dom::bindings::proxyhandler::fill_property_descriptor',
diff --git a/components/script/dom/comment.rs b/components/script/dom/comment.rs
index b135def6e2ad..9efe8c8164cc 100644
--- a/components/script/dom/comment.rs
+++ b/components/script/dom/comment.rs
@@ -9,8 +9,8 @@ use dom::bindings::js::Root;
 use dom::bindings::str::DOMString;
 use dom::characterdata::CharacterData;
 use dom::document::Document;
-use dom::globalscope::GlobalScope;
 use dom::node::Node;
+use dom::window::Window;
 
 /// An HTML comment.
 #[dom_struct]
@@ -31,8 +31,8 @@ impl Comment {
                            CommentBinding::Wrap)
     }
 
-    pub fn Constructor(global: &GlobalScope, data: DOMString) -> Fallible<Root<Comment>> {
-        let document = global.as_window().Document();
+    pub fn Constructor(window: &Window, data: DOMString) -> Fallible<Root<Comment>> {
+        let document = window.Document();
         Ok(Comment::new(data, &document))
     }
 }
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 0bf77ccf73dc..a9813c912d39 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -1917,11 +1917,10 @@ impl Document {
     }
 
     // https://dom.spec.whatwg.org/#dom-document
-    pub fn Constructor(global: &GlobalScope) -> Fallible<Root<Document>> {
-        let win = global.as_window();
-        let doc = win.Document();
+    pub fn Constructor(window: &Window) -> Fallible<Root<Document>> {
+        let doc = window.Document();
         let docloader = DocumentLoader::new(&*doc.loader());
-        Ok(Document::new(win,
+        Ok(Document::new(window,
                          None,
                          None,
                          IsHTMLDocument::NonHTMLDocument,
diff --git a/components/script/dom/documentfragment.rs b/components/script/dom/documentfragment.rs
index 334e083f1b7b..554fb8fe3b3b 100644
--- a/components/script/dom/documentfragment.rs
+++ b/components/script/dom/documentfragment.rs
@@ -12,10 +12,10 @@ use dom::bindings::js::Root;
 use dom::bindings::str::DOMString;
 use dom::document::Document;
 use dom::element::Element;
-use dom::globalscope::GlobalScope;
 use dom::htmlcollection::HTMLCollection;
 use dom::node::{Node, window_from_node};
 use dom::nodelist::NodeList;
+use dom::window::Window;
 use servo_atoms::Atom;
 
 // https://dom.spec.whatwg.org/#documentfragment
@@ -38,8 +38,8 @@ impl DocumentFragment {
                            DocumentFragmentBinding::Wrap)
     }
 
-    pub fn Constructor(global: &GlobalScope) -> Fallible<Root<DocumentFragment>> {
-        let document = global.as_window().Document();
+    pub fn Constructor(window: &Window) -> Fallible<Root<DocumentFragment>> {
+        let document = window.Document();
 
         Ok(DocumentFragment::new(&document))
     }
diff --git a/components/script/dom/domparser.rs b/components/script/dom/domparser.rs
index 2a770aeb3a03..0ce2d50e09ad 100644
--- a/components/script/dom/domparser.rs
+++ b/components/script/dom/domparser.rs
@@ -17,7 +17,6 @@ use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
 use dom::document::{Document, IsHTMLDocument};
 use dom::document::DocumentSource;
-use dom::globalscope::GlobalScope;
 use dom::servoparser::ServoParser;
 use dom::window::Window;
 
@@ -41,8 +40,8 @@ impl DOMParser {
                            DOMParserBinding::Wrap)
     }
 
-    pub fn Constructor(global: &GlobalScope) -> Fallible<Root<DOMParser>> {
-        Ok(DOMParser::new(global.as_window()))
+    pub fn Constructor(window: &Window) -> Fallible<Root<DOMParser>> {
+        Ok(DOMParser::new(window))
     }
 }
 
diff --git a/components/script/dom/extendableevent.rs b/components/script/dom/extendableevent.rs
index 55e9500a8e44..0a7db40b6d55 100644
--- a/components/script/dom/extendableevent.rs
+++ b/components/script/dom/extendableevent.rs
@@ -10,7 +10,7 @@ use dom::bindings::js::Root;
 use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::Event;
-use dom::globalscope::GlobalScope;
+use dom::serviceworkerglobalscope::ServiceWorkerGlobalScope;
 use js::jsapi::{HandleValue, JSContext};
 use servo_atoms::Atom;
 
@@ -28,12 +28,12 @@ impl ExtendableEvent {
             extensions_allowed: true
         }
     }
-    pub fn new(global: &GlobalScope,
+    pub fn new(worker: &ServiceWorkerGlobalScope,
                type_: Atom,
                bubbles: bool,
                cancelable: bool)
                -> Root<ExtendableEvent> {
-        let ev = reflect_dom_object(box ExtendableEvent::new_inherited(), global, ExtendableEventBinding::Wrap);
+        let ev = reflect_dom_object(box ExtendableEvent::new_inherited(), worker, ExtendableEventBinding::Wrap);
         {
             let event = ev.upcast::<Event>();
             event.init_event(type_, bubbles, cancelable);
@@ -41,10 +41,10 @@ impl ExtendableEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(worker: &ServiceWorkerGlobalScope,
                        type_: DOMString,
                        init: &ExtendableEventBinding::ExtendableEventInit) -> Fallible<Root<ExtendableEvent>> {
-        Ok(ExtendableEvent::new(global,
+        Ok(ExtendableEvent::new(worker,
                                 Atom::from(type_),
                                 init.parent.bubbles,
                                 init.parent.cancelable))
diff --git a/components/script/dom/extendablemessageevent.rs b/components/script/dom/extendablemessageevent.rs
index fbbdd59cbd31..8f156a8f4d35 100644
--- a/components/script/dom/extendablemessageevent.rs
+++ b/components/script/dom/extendablemessageevent.rs
@@ -13,6 +13,7 @@ use dom::event::Event;
 use dom::eventtarget::EventTarget;
 use dom::extendableevent::ExtendableEvent;
 use dom::globalscope::GlobalScope;
+use dom::serviceworkerglobalscope::ServiceWorkerGlobalScope;
 use js::jsapi::{HandleValue, Heap, JSContext};
 use js::jsval::JSVal;
 use servo_atoms::Atom;
@@ -46,10 +47,11 @@ impl ExtendableMessageEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(worker: &ServiceWorkerGlobalScope,
                        type_: DOMString,
                        init: &ExtendableMessageEventBinding::ExtendableMessageEventInit)
                        -> Fallible<Root<ExtendableMessageEvent>> {
+        let global = worker.upcast::<GlobalScope>();
         rooted!(in(global.get_cx()) let data = init.data);
         let ev = ExtendableMessageEvent::new(global,
                                              Atom::from(type_),
diff --git a/components/script/dom/focusevent.rs b/components/script/dom/focusevent.rs
index d06b725286d7..1eb3983737d8 100644
--- a/components/script/dom/focusevent.rs
+++ b/components/script/dom/focusevent.rs
@@ -53,12 +53,12 @@ impl FocusEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &FocusEventBinding::FocusEventInit) -> Fallible<Root<FocusEvent>> {
         let bubbles = EventBubbles::from(init.parent.parent.bubbles);
         let cancelable = EventCancelable::from(init.parent.parent.cancelable);
-        let event = FocusEvent::new(global.as_window(),
+        let event = FocusEvent::new(window,
                                     type_,
                                     bubbles,
                                     cancelable,
diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index 3b58b383bf4f..a86f0258918f 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -16,11 +16,11 @@ use dom::bindings::str::DOMString;
 use dom::document::Document;
 use dom::element::{AttributeMutation, Element, RawLayoutElementHelpers};
 use dom::eventtarget::EventTarget;
-use dom::globalscope::GlobalScope;
 use dom::htmlelement::HTMLElement;
 use dom::node::{Node, NodeDamage, document_from_node, window_from_node};
 use dom::values::UNSIGNED_LONG_MAX;
 use dom::virtualmethods::VirtualMethods;
+use dom::window::Window;
 use html5ever_atoms::LocalName;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
@@ -220,10 +220,10 @@ impl HTMLImageElement {
                            HTMLImageElementBinding::Wrap)
     }
 
-    pub fn Image(global: &GlobalScope,
+    pub fn Image(window: &Window,
                  width: Option<u32>,
                  height: Option<u32>) -> Fallible<Root<HTMLImageElement>> {
-        let document = global.as_window().Document();
+        let document = window.Document();
         let image = HTMLImageElement::new(local_name!("img"), None, &document);
         if let Some(w) = width {
             image.SetWidth(w);
diff --git a/components/script/dom/keyboardevent.rs b/components/script/dom/keyboardevent.rs
index 4da24309e189..99cc61e021f2 100644
--- a/components/script/dom/keyboardevent.rs
+++ b/components/script/dom/keyboardevent.rs
@@ -12,7 +12,6 @@ use dom::bindings::js::{Root, RootedReference};
 use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::Event;
-use dom::globalscope::GlobalScope;
 use dom::uievent::UIEvent;
 use dom::window::Window;
 use msg::constellation_msg;
@@ -101,10 +100,10 @@ impl KeyboardEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &KeyboardEventBinding::KeyboardEventInit) -> Fallible<Root<KeyboardEvent>> {
-        let event = KeyboardEvent::new(global.as_window(),
+        let event = KeyboardEvent::new(window,
                                        type_,
                                        init.parent.parent.parent.bubbles,
                                        init.parent.parent.parent.cancelable,
diff --git a/components/script/dom/mouseevent.rs b/components/script/dom/mouseevent.rs
index 27a61c79400b..2b39d5552044 100644
--- a/components/script/dom/mouseevent.rs
+++ b/components/script/dom/mouseevent.rs
@@ -12,7 +12,6 @@ use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::{Event, EventBubbles, EventCancelable};
 use dom::eventtarget::EventTarget;
-use dom::globalscope::GlobalScope;
 use dom::uievent::UIEvent;
 use dom::window::Window;
 use std::cell::Cell;
@@ -82,12 +81,12 @@ impl MouseEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &MouseEventBinding::MouseEventInit) -> Fallible<Root<MouseEvent>> {
         let bubbles = EventBubbles::from(init.parent.parent.parent.bubbles);
         let cancelable = EventCancelable::from(init.parent.parent.parent.cancelable);
-        let event = MouseEvent::new(global.as_window(),
+        let event = MouseEvent::new(window,
                                     type_,
                                     bubbles,
                                     cancelable,
diff --git a/components/script/dom/range.rs b/components/script/dom/range.rs
index 8e8b9888b87d..0a5ab7a66dff 100644
--- a/components/script/dom/range.rs
+++ b/components/script/dom/range.rs
@@ -22,11 +22,11 @@ use dom::characterdata::CharacterData;
 use dom::document::Document;
 use dom::documentfragment::DocumentFragment;
 use dom::element::Element;
-use dom::globalscope::GlobalScope;
 use dom::htmlbodyelement::HTMLBodyElement;
 use dom::htmlscriptelement::HTMLScriptElement;
 use dom::node::{Node, UnbindContext};
 use dom::text::Text;
+use dom::window::Window;
 use heapsize::HeapSizeOf;
 use js::jsapi::JSTracer;
 use std::cell::{Cell, UnsafeCell};
@@ -70,8 +70,8 @@ impl Range {
     }
 
     // https://dom.spec.whatwg.org/#dom-range
-    pub fn Constructor(global: &GlobalScope) -> Fallible<Root<Range>> {
-        let document = global.as_window().Document();
+    pub fn Constructor(window: &Window) -> Fallible<Root<Range>> {
+        let document = window.Document();
         Ok(Range::new_with_doc(&document))
     }
 
diff --git a/components/script/dom/serviceworkerglobalscope.rs b/components/script/dom/serviceworkerglobalscope.rs
index a38770641316..b39faeb5694d 100644
--- a/components/script/dom/serviceworkerglobalscope.rs
+++ b/components/script/dom/serviceworkerglobalscope.rs
@@ -319,7 +319,7 @@ impl ServiceWorkerGlobalScope {
     }
 
     fn dispatch_activate(&self) {
-        let event = ExtendableEvent::new(self.upcast(), atom!("activate"), false, false);
+        let event = ExtendableEvent::new(self, atom!("activate"), false, false);
         let event = (&*event).upcast::<Event>();
         self.upcast::<EventTarget>().dispatch_event(event);
     }
diff --git a/components/script/dom/text.rs b/components/script/dom/text.rs
index a6034a7dad5d..cfa670d9acb9 100644
--- a/components/script/dom/text.rs
+++ b/components/script/dom/text.rs
@@ -14,8 +14,8 @@ use dom::bindings::js::RootedReference;
 use dom::bindings::str::DOMString;
 use dom::characterdata::CharacterData;
 use dom::document::Document;
-use dom::globalscope::GlobalScope;
 use dom::node::Node;
+use dom::window::Window;
 
 /// An HTML text node.
 #[dom_struct]
@@ -35,8 +35,8 @@ impl Text {
                            document, TextBinding::Wrap)
     }
 
-    pub fn Constructor(global: &GlobalScope, text: DOMString) -> Fallible<Root<Text>> {
-        let document = global.as_window().Document();
+    pub fn Constructor(window: &Window, text: DOMString) -> Fallible<Root<Text>> {
+        let document = window.Document();
         Ok(Text::new(text, &document))
     }
 }
diff --git a/components/script/dom/transitionevent.rs b/components/script/dom/transitionevent.rs
index 1f487cb38a57..cc17e77eae16 100644
--- a/components/script/dom/transitionevent.rs
+++ b/components/script/dom/transitionevent.rs
@@ -13,6 +13,7 @@ use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::Event;
 use dom::globalscope::GlobalScope;
+use dom::window::Window;
 use servo_atoms::Atom;
 
 #[dom_struct]
@@ -46,9 +47,10 @@ impl TransitionEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &TransitionEventInit) -> Fallible<Root<TransitionEvent>> {
+        let global = window.upcast::<GlobalScope>();
         Ok(TransitionEvent::new(global, Atom::from(type_), init))
     }
 }
diff --git a/components/script/dom/uievent.rs b/components/script/dom/uievent.rs
index 08e1b0c912c7..289088b29771 100644
--- a/components/script/dom/uievent.rs
+++ b/components/script/dom/uievent.rs
@@ -12,7 +12,6 @@ use dom::bindings::js::Root;
 use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::globalscope::GlobalScope;
 use dom::window::Window;
 use servo_atoms::Atom;
 use std::cell::Cell;
@@ -52,12 +51,12 @@ impl UIEvent {
         ev
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &UIEventBinding::UIEventInit) -> Fallible<Root<UIEvent>> {
         let bubbles = EventBubbles::from(init.parent.bubbles);
         let cancelable = EventCancelable::from(init.parent.cancelable);
-        let event = UIEvent::new(global.as_window(),
+        let event = UIEvent::new(window,
                                  type_,
                                  bubbles, cancelable,
                                  init.view.r(), init.detail);
diff --git a/components/script/dom/webglcontextevent.rs b/components/script/dom/webglcontextevent.rs
index c128515e81a2..3de8efa43541 100644
--- a/components/script/dom/webglcontextevent.rs
+++ b/components/script/dom/webglcontextevent.rs
@@ -13,6 +13,7 @@ use dom::bindings::reflector::reflect_dom_object;
 use dom::bindings::str::DOMString;
 use dom::event::{Event, EventBubbles, EventCancelable};
 use dom::globalscope::GlobalScope;
+use dom::window::Window;
 use servo_atoms::Atom;
 
 #[dom_struct]
@@ -52,14 +53,14 @@ impl WebGLContextEvent {
                         WebGLContextEventBinding::Wrap)
     }
 
-    pub fn new(global: &GlobalScope,
+    pub fn new(window: &Window,
                type_: Atom,
                bubbles: EventBubbles,
                cancelable: EventCancelable,
                status_message: DOMString) -> Root<WebGLContextEvent> {
         let event = reflect_dom_object(
                         box WebGLContextEvent::new_inherited(status_message),
-                        global,
+                        window,
                         WebGLContextEventBinding::Wrap);
 
         {
@@ -70,7 +71,7 @@ impl WebGLContextEvent {
         event
     }
 
-    pub fn Constructor(global: &GlobalScope,
+    pub fn Constructor(window: &Window,
                        type_: DOMString,
                        init: &WebGLContextEventInit) -> Fallible<Root<WebGLContextEvent>> {
         let status_message = match init.statusMessage.as_ref() {
@@ -82,7 +83,7 @@ impl WebGLContextEvent {
 
         let cancelable = EventCancelable::from(init.parent.cancelable);
 
-        Ok(WebGLContextEvent::new(global,
+        Ok(WebGLContextEvent::new(window,
                                   Atom::from(type_),
                                   bubbles,
                                   cancelable,
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index 5428fc794fae..47a139cc1b08 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -172,7 +172,7 @@ impl WebGLRenderingContext {
             Ok(ctx) => Some(reflect_dom_object(box ctx, global, WebGLRenderingContextBinding::Wrap)),
             Err(msg) => {
                 error!("Couldn't create WebGLRenderingContext: {}", msg);
-                let event = WebGLContextEvent::new(global,
+                let event = WebGLContextEvent::new(global.as_window(),
                                                    atom!("webglcontextcreationerror"),
                                                    EventBubbles::DoesNotBubble,
                                                    EventCancelable::Cancelable,
diff --git a/components/script/dom/webidls/DOMMatrix.webidl b/components/script/dom/webidls/DOMMatrix.webidl
index d8306d315fb6..f664e7b77b21 100644
--- a/components/script/dom/webidls/DOMMatrix.webidl
+++ b/components/script/dom/webidls/DOMMatrix.webidl
@@ -12,8 +12,8 @@
 
 [Constructor,
 // Constructor(DOMString transformList),
-Constructor(sequence<unrestricted double> numberSequence)
-// Exposed=(Window,Worker)
+Constructor(sequence<unrestricted double> numberSequence),
+Exposed=(Window,Worker)
 ]
 interface DOMMatrix : DOMMatrixReadOnly {
 
diff --git a/components/script/dom/webidls/DOMMatrixReadOnly.webidl b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
index 6d92a6b08289..b469b1413ece 100644
--- a/components/script/dom/webidls/DOMMatrixReadOnly.webidl
+++ b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
@@ -13,7 +13,7 @@
 [Constructor,
 // Constructor(DOMString transformList)
 Constructor(sequence<unrestricted double> numberSequence),
-// Exposed=(Window,Worker)
+Exposed=(Window,Worker)
 ]
 interface DOMMatrixReadOnly {