Move paintWorklet from "Window" to "CSS" according to new specification

Relevant discussion: https://github.com/w3c/css-houdini-drafts/issues/410

components/script/dom/css.rs

@@ -6,8 +6,10 @@ use cssparser::{Parser, ParserInput, serialize_identifier};
 use dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::WindowMethods;
 use dom::bindings::error::Fallible;
 use dom::bindings::reflector::Reflector;
+use dom::bindings::root::DomRoot;
 use dom::bindings::str::DOMString;
 use dom::window::Window;
+use dom::worklet::Worklet;
 use dom_struct::dom_struct;
 use style::context::QuirksMode;
 use style::parser::ParserContext;
@@ -63,4 +65,9 @@ impl CSS {
             false
         }
     }
+
+    /// <https://drafts.css-houdini.org/css-paint-api-1/#paint-worklet>
+    pub fn PaintWorklet(win: &Window) -> DomRoot<Worklet> {
+        win.paint_worklet()
+    }
 }

components/script/dom/webidls/CSS.webidl

@@ -17,3 +17,8 @@ partial interface CSS {
   static boolean supports(DOMString property, DOMString value);
   static boolean supports(DOMString conditionText);
 };
+
+// https://drafts.css-houdini.org/css-paint-api-1/#paint-worklet
+partial interface CSS {
+    [SameObject, Pref="dom.worklet.enabled"] static readonly attribute Worklet paintWorklet;
+};

components/script/dom/webidls/Window.webidl

@@ -196,8 +196,3 @@ partial interface Window {
    readonly attribute TestRunner testRunner;
    //readonly attribute EventSender eventSender;
 };
-
-// https://drafts.css-houdini.org/css-paint-api-1/#paint-worklet
-partial interface Window {
-    [SameObject, Pref="dom.worklet.enabled"] readonly attribute Worklet paintWorklet;
-};

components/script/dom/window.rs

@@ -1022,17 +1022,17 @@ impl WindowMethods for Window {
         fetch::Fetch(&self.upcast(), input, init)
     }
 
-    // https://drafts.css-houdini.org/css-paint-api-1/#paint-worklet
-    fn PaintWorklet(&self) -> DomRoot<Worklet> {
-        self.paint_worklet.or_init(|| self.new_paint_worklet())
-    }
-
     fn TestRunner(&self) -> DomRoot<TestRunner> {
         self.test_runner.or_init(|| TestRunner::new(self.upcast()))
     }
 }
 
 impl Window {
+    // https://drafts.css-houdini.org/css-paint-api-1/#paint-worklet
+    pub fn paint_worklet(&self) -> DomRoot<Worklet> {
+        self.paint_worklet.or_init(|| self.new_paint_worklet())
+    }
+
     pub fn task_canceller(&self) -> TaskCanceller {
         TaskCanceller {
             cancelled: Some(self.ignore_further_async_events.borrow().clone()),

tests/wpt/mozilla/tests/mozilla/css-paint-api/css-paint-tests.js

@@ -2,11 +2,11 @@
 // requestAnimationFrame. In the second frame, we take a screenshot, that makes
 // sure that we already have a full frame.
 function importPaintWorkletAndTerminateTestAfterAsyncPaint(code) {
-    if (typeof paintWorklet == "undefined") {
+    if (typeof CSS.paintWorklet == "undefined") {
         takeScreenshot();
     } else {
         var blob = new Blob([code], {type: 'text/javascript'});
-        paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
+        CSS.paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
             requestAnimationFrame(function() {
                 requestAnimationFrame(function() {
                     takeScreenshot();

tests/wpt/mozilla/tests/mozilla/css-paint-api/valid-image-after-load.html

@@ -30,7 +30,7 @@ if (window.testRunner) {
 var blob = new Blob([document.getElementById('code').textContent],
                     {type: 'text/javascript'});
 var frame_cnt = 0;
-paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
+CSS.paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
     var el = document.getElementById('output');
     el.style.backgroundImage = 'paint(green)';
     requestAnimationFrame(function() {

tests/wpt/mozilla/tests/mozilla/css-paint-api/valid-image-before-load.html

@@ -33,7 +33,7 @@ el.style.backgroundImage = 'paint(green)';
 var blob = new Blob([document.getElementById('code').textContent],
                     {type: 'text/javascript'});
 var frame_cnt = 0;
-paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
+CSS.paintWorklet.addModule(URL.createObjectURL(blob)).then(function() {
     requestAnimationFrame(function() {
         takeScreenshot(frame_cnt);
     });