Auto merge of #22743 - ferjm:shadowdom, r=emilio

Partial ShadowDOM support

This is just an early WIP, not to take it very seriously yet.

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [x] These changes fix #22719
- [x] There are tests for these changes

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components/script/dom/webidls/Document.webidl

@@ -132,7 +132,6 @@ partial /*sealed*/ interface Document {
 
   // user interaction
   readonly attribute Window?/*Proxy?*/ defaultView;
-  readonly attribute Element? activeElement;
   boolean hasFocus();
   // [CEReactions]
   // attribute DOMString designMode;
@@ -199,17 +198,6 @@ partial interface Document {
       TouchList createTouchList(Touch... touches);
 };
 
-// https://drafts.csswg.org/cssom-view/#dom-document-elementfrompoint
-partial interface Document {
-  Element? elementFromPoint(double x, double y);
-  sequence<Element> elementsFromPoint(double x, double y);
-};
-
-// https://drafts.csswg.org/cssom/#extensions-to-the-document-interface
-partial interface Document {
-  [SameObject] readonly attribute StyleSheetList styleSheets;
-};
-
 // https://fullscreen.spec.whatwg.org/#api
 partial interface Document {
   [LenientSetter] readonly attribute boolean fullscreenEnabled;
@@ -221,3 +209,5 @@ partial interface Document {
   attribute EventHandler onfullscreenchange;
   attribute EventHandler onfullscreenerror;
 };
+
+Document implements DocumentOrShadowRoot;

components/script/dom/webidls/DocumentOrShadowRoot.webidl

@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+/*
+ * The origin of this IDL file is
+ * https://dom.spec.whatwg.org/#documentorshadowroot
+ * https://w3c.github.io/webcomponents/spec/shadow/#extensions-to-the-documentorshadowroot-mixin
+ */
+
+[NoInterfaceObject]
+interface DocumentOrShadowRoot {
+  // Selection? getSelection();
+  Element? elementFromPoint (double x, double y);
+  sequence<Element> elementsFromPoint (double x, double y);
+  // CaretPosition? caretPositionFromPoint (double x, double y);
+  readonly attribute Element? activeElement;
+  readonly attribute StyleSheetList styleSheets;
+};

components/script/dom/webidls/Element.webidl

@@ -81,6 +81,8 @@ interface Element : Node {
   void insertAdjacentText(DOMString where_, DOMString data);
   [CEReactions, Throws]
   void insertAdjacentHTML(DOMString position, DOMString html);
+
+  [Throws, Pref="dom.shadowdom.enabled"] ShadowRoot attachShadow();
 };
 
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-element-interface

components/script/dom/webidls/Node.webidl

@@ -32,7 +32,7 @@ interface Node : EventTarget {
   readonly attribute Document? ownerDocument;
 
   [Pure]
-  Node getRootNode();
+  Node getRootNode(optional GetRootNodeOptions options);
 
   [Pure]
   readonly attribute Node? parentNode;
@@ -58,7 +58,7 @@ interface Node : EventTarget {
   [CEReactions]
   void normalize();
 
-  [CEReactions]
+  [CEReactions, Throws]
   Node cloneNode(optional boolean deep = false);
   [Pure]
   boolean isEqualNode(Node? node);
@@ -92,3 +92,7 @@ interface Node : EventTarget {
   [CEReactions, Throws]
   Node removeChild(Node child);
 };
+
+dictionary GetRootNodeOptions {
+  boolean composed = false;
+};

components/script/dom/webidls/ShadowRoot.webidl

@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+/*
+ * The origin of this IDL file is:
+ * https://dom.spec.whatwg.org/#interface-shadowroot
+ */
+
+[Exposed=Window]
+interface ShadowRoot : DocumentFragment {
+  readonly attribute ShadowRootMode mode;
+  readonly attribute Element host;
+};
+
+enum ShadowRootMode { "open", "closed"};
+
+ShadowRoot implements DocumentOrShadowRoot;