Auto merge of #29396 - delan:window-getter, r=jdm

HTML #named-access-on-the-window-object This patch implements [named access on the window object](https://html.spec.whatwg.org/#named-access-on-the-window-object) based on @pylbrecht’s and @yvt’s previous work (see also #27952, #25562, #21869, #19904). That work makes 130 tests pass, and I’ve made some additional changes to make [the test for the feature itself](https://wpt.live/webidl/ecmascript-binding/window-named-properties-object.html) pass too, but I haven’t worked with mozjs before, so I have no idea if I’ve gone about my changes the Right Way. In particular, this patch: * [x] applies @pylbrecht’s patch (#27952) * [x] resolves conflicts related to #29079 and #28546 (5ae0ca48f8a74e4bae04f8bc9e50252a05e4c1e1) * [x] applies @yvt’s patch to the segfault in getPrototypeIfOrdinary (1e24ffdec6e91784b76a8f02bda26e8de0420c94) * [x] reverts the change introducing Untransplantable (76dc35a2b4ddd39f588b6c0b4e9bd46346888606), since #28534 was abandoned in favour of #28536 * [x] triages the unexpected WPT results, updating expectations as needed (see below) * [x] fixes the failures in /webidl/ecmascript-binding/window-named-properties-object.html (3844f69ea9b591b766fee3537f640e7aae05bb11) * [x] fixes the failures in the [[GetOwnProperty]] subtest (75c24e9c134c531f8fc893a185683ea2e609a47e) * [x] fixes the failures in the [[DefineOwnProperty]] subtest (e4e7a14e514db75c3d6694fb1aaeb24d04c9ae81) * [x] fixes the failures in the [[HasProperty]] subtest (75c24e9c134c531f8fc893a185683ea2e609a47e) * [x] fixes the failures in the [[Get]] subtest (4bafb273d0d1d57589cede88ba2696b0e42920a9) * [x] fixes the failures in the [[Set]] (direct) subtest (e4e7a14e514db75c3d6694fb1aaeb24d04c9ae81) * [x] fixes the failures in the [[Delete]] subtest (4bafb273d0d1d57589cede88ba2696b0e42920a9) * [x] fixes the failures in the [[OwnPropertyKeys]] subtest (afcd24a2973557509438833b8fe06a24377710f1) * [x] resolves the todos and fixmes * [x] Document: handle exposed objects ×3 (ed3e37bb22276031e0423dfa8005bc79ab673913) * [x] Window::NamedGetter: document.get_elements_with_id() (618ef5744645bb14405d95177bf49aa3b98439dc) * [x] get_own_property_descriptor: check for interactions with indexed access (b906faee59aa15f716662c223fc61758c4053299) * [x] create trap: pass proper classp (618ef5744645bb14405d95177bf49aa3b98439dc) <details><summary>131× tests that now pass</summary> * **/webidl/ecmascript-binding/window-named-properties-object.html** *directly relevant to this patch* * **/FileAPI/Blob-methods-from-detached-frame.html** done #29450 #29451 * **/cors/script-304.html** * **/css/CSS2/abspos/adjacent-to-relpos-inline-in-inline-that-had-block.html** * **/css/CSS2/abspos/adjacent-to-relpos-inline-that-had-block.html** * **/css/CSS2/floats-clear/remove-block-before-self-collapsing-sibling-with-clearance.html** * **/css/CSS2/floats/computed-float-position-absolute.html** * **/css/CSS2/normal-flow/block-in-inline-hittest-float-001.html** * **/css/CSS2/normal-flow/block-in-inline-insert-018.html** * **/css/CSS2/normal-flow/margin-collapse-through-percentage-padding.html** * **/css/CSS2/positioning/abspos-change-in-inline-block.html** * **/css/CSS2/positioning/abspos-width-change-inline-container-001.html** * **/css/CSS2/positioning/detach-abspos-before-layout.html** * **/css/CSS2/positioning/relpos-percentage-left-in-scrollable-2.html** * **/css/CSS2/positioning/relpos-percentage-left-in-scrollable.html** * **/css/CSS2/stacking-context/composite-change-after-scroll-preserves-stacking-order.html** * **/css/CSS2/stacking-context/opacity-change-parent-stacking-context.html** * **/css/CSS2/stacking-context/opacity-change-twice-stacking-context.html** * **/css/CSS2/stacking-context/opacity-transition-change-parent-stacking-context.html** * **/css/css-animations/animation-base-response-002.html** * **/css/css-animations/style-animation-parsing.html** * **/css/css-backgrounds/background-clip-color-repaint.html** * **/css/css-backgrounds/background-image-gradient-currentcolor-conic-repaint.html** * **/css/css-backgrounds/background-image-gradient-currentcolor-linear-repaint.html** * **/css/css-backgrounds/background-image-gradient-currentcolor-radial-repaint.html** * **/css/css-backgrounds/background-image-none-gradient-repaint.html** * **/css/css-backgrounds/border-radius-dynamic-from-no-radius.html** * **/css/css-backgrounds/child-move-reveals-parent-background.html** * **/css/css-color/filters-under-will-change-opacity.html** * **/css/css-flexbox/anonymous-flex-item-001.html** * **/css/css-flexbox/anonymous-flex-item-003.html** * **/css/css-flexbox/dynamic-bsize-change.html** * **/css/css-flexbox/flex-aspect-ratio-img-row-016.html** * **/css/cssom/at-namespace.html** * **/css/cssom/computed-style-002.html** * **/css/cssom/getComputedStyle-display-none-002.html** * **/css/cssom/getComputedStyle-display-none-003.html** * **/css/cssom/preferred-stylesheet-reversed-order.html** * **/css/cssom-view/HTMLImageElement-x-and-y-ignore-transforms.html** * **/css/cssom-view/pt-to-px-width.html** * **/css/cssom-view/scroll-back-to-initial-position.html** * **/css/css-text-decor/text-decoration-color-recalc-002.html** * **/css/css-text-decor/text-decoration-line-grammar-error-color-dynamic-001.optional.html** * **/css/css-text-decor/text-decoration-line-spelling-error-color-dynamic-001.optional.html** * **/css/css-text/text-indent/percentage-value-intrinsic-size.html** * **/css/css-text/white-space/display-contents-remove-whitespace-change.html** * **/css/css-text/white-space/white-space-empty-text-sibling.html** * **/css/css-transforms/change-perspective-property.html** * **/css/css-transforms/change-scale-wide-range.html** * **/css/css-transforms/change-transform-origin-property.html** * **/css/css-transforms/dynamic-fixed-pos-cb-change.html** * **/css/css-transforms/individual-transform/change-rotate-property.html** * **/css/css-transforms/individual-transform/change-scale-property.html** * **/css/css-transforms/paint-order-with-transform-change.html** * **/css/css-transforms/size-change-under-backface-visibility-hidden.html** * **/css/css-transforms/subpixel-transform-changes-001.html** * **/css/css-transforms/subpixel-transform-changes-002.html** * **/css/css-transforms/subpixel-transform-changes-003.html** * **/css/css-transforms/subpixel-transform-changes-004.html** * **/css/css-transitions/transition-reparented.html** * **/css/css-ui/historical/moz-user-modify-01.html** * **/css/css-ui/historical/user-modify-01.html** * **/css/css-ui/historical/webkit-user-modify-01.html** * **/css/css-ui/resize-change-margin.html** * **/css/css-ui/text-overflow-change-color.html** * **/css/css-ui/text-overflow-ellipsis-width-001.html** * **/css/css-values/animations/line-height-lh-transition.html** * **/css/css-values/calc-nesting.html** * **/css/css-values/update-subpixel-rem-unit.html** * **/css/css-values/viewport-units-modify.html** * **/css/css-variables/css-variable-change-style-001.html** * **/css/css-variables/css-variable-change-style-002.html** * **/css/css-variables/variable-cycles.html** * **/css/selectors/attribute-selectors/style-attribute-selector.html** * **/css/selectors/i18n/lang-pseudo-class-disconnected.html** * **/css/selectors/invalidation/attribute.html** * **/css/selectors/invalidation/class-id-attr.html** * **/css/selectors/invalidation/defined.html** * **/css/selectors/invalidation/sheet-going-away-001.html** * **/css/selectors/invalidation/sibling.html** * **/css/selectors/missing-right-token.html** * **/css/selectors/not-complex.html** * **/css/selectors/not-specificity.html** * **/css/selectors/nth-of-type-namespace.html** * **/css/selectors/selectors-case-sensitive-001.html** * **/css/selectors/visited-inheritance.html** * **/custom-elements/CustomElementRegistry-constructor-and-callbacks-are-held-strongly.html** * **/dom/events/event-global-is-still-set-when-coercing-beforeunload-result.html** * **/dom/nodes/remove-and-adopt-thcrash.html** * **/html/browsers/browsing-the-web/history-traversal/history-traversal-navigate-parent-while-child-loading.html** * **/html/browsers/history/the-history-interface/history_back_cross_realm_method.html** * **/html/browsers/history/the-history-interface/history_forward_cross_realm_method.html** * **/html/browsers/history/the-history-interface/history_go_cross_realm_method.html** * **/html/browsers/the-window-object/named-access-on-the-window-object/window-named-properties.html** * **/html/dom/elements/images/bypass-cache-revalidation.html** * **/html/rendering/non-replaced-elements/tables/table-ua-stylesheet.html** * **/html/rendering/replaced-elements/attributes-for-embedded-content-and-images/img-alt-crash-001.html** * **/html/rendering/replaced-elements/embedded-content/change-src-while-not-displayed.html** * **/html/rendering/replaced-elements/embedded-content/cross-domain-iframe-in-multicol.sub.html** * **/html/rendering/replaced-elements/embedded-content/cross-domain-iframe.sub.html** * **/html/rendering/replaced-elements/embedded-content/tall-cross-domain-iframe-in-scrolled.sub.html** * **/html/rendering/widgets/the-select-element/select-invalidation.html** * **/html/semantics/document-metadata/the-base-element/base_target_does_not_affect_iframe_src_navigation.html** * **/html/semantics/document-metadata/the-base-element/base_target_does_not_affect_location_assignment.html** * **/html/semantics/embedded-content/the-embed-element/embed-document-under-content-visibility-focus.html** * **/html/semantics/embedded-content/the-embed-element/embed-document-under-content-visibility-gbcr.html** * **/html/semantics/embedded-content/the-iframe-element/iframe-network-error.sub.html** * **/html/semantics/embedded-content/the-iframe-element/srcdoc-anchor.html** * **/html/semantics/embedded-content/the-iframe-element/srcdoc-attribute-reset.html** * **/html/semantics/embedded-content/the-img-element/image-compositing-change.html** * **/html/semantics/embedded-content/the-img-element/image-compositing-large-scale-change.html** * **/html/semantics/embedded-content/the-img-element/image-loading-lazy-clip-path.html** * **/html/semantics/embedded-content/the-img-element/image-loading-lazy-zero-intersection-area.html** * **/html/semantics/embedded-content/the-img-element/image-loading-subpixel-clip.html** * **/html/semantics/forms/form-submission-0/form-double-submit-to-different-origin-frame.html** * **/html/semantics/forms/form-submission-0/form-submit-iframe-then-location-navigate.html** * **/html/semantics/forms/form-submission-0/reparent-form-during-planned-navigation-task.html** * **/html/semantics/forms/the-button-element/button-willvalidate-readonly-attribute.html** * **/html/semantics/forms/the-input-element/datetime-local-trailing-zeros.html** * **/html/semantics/forms/the-input-element/radio-morphed.html** * **/html/semantics/forms/the-progress-element/progress.html** * **/html/semantics/forms/the-select-element/select-willvalidate-readonly-attribute.html** * **/html/semantics/selectors/pseudo-classes/placeholder-shown-type-change.html** * **/html/syntax/serializing-html-fragments/initial-linefeed-pre.html** * **/html/webappapis/scripting/events/event-handler-processing-algorithm-error/frameset-element-synthetic-errorevent.html** * **/html/webappapis/scripting/events/event-handler-processing-algorithm-error/frameset-element-synthetic-event.html** * **/quirks/unitless-length/excluded-properties-001.html** * **/quirks/unitless-length/excluded-properties-003.html** * **/selection/caret/empty-elements.html** * **/selection/contenteditable/cefalse-on-boundaries.html** * **/selection/textcontrols/onselectionchange-content-attribute.html** </details> <details><summary>94× tests that improve but still fail in a way that’s clearly the subject of the test</summary> * **/css/css-animations/animation-base-response-001.html** * **/css/css-backgrounds/background-image-gradient-currentcolor-visited.html** * **/css/css-backgrounds/inheritance.sub.html** * **/css/css-backgrounds/local-attachment-content-box-scroll.html** * **/css/css-color/canvas-change-opacity.html** * **/css/css-color/color-initial-canvastext.html** * **/css/css-flexbox/flex-aspect-ratio-img-column-010.html** * **/css/css-flexbox/flex-aspect-ratio-img-row-004.html** * **/css/css-fonts/parsing/font-face-src-format.html** getter works but insertRule does nothing * **/css/css-fonts/parsing/font-face-src-list.html** as above * **/css/css-fonts/parsing/font-face-src-local.html** as above, but also delayed length change? * **/css/css-fonts/parsing/font-face-src-tech.html** as above * **/css/css-text/white-space/trailing-space-before-br-001.html** * **/css/css-transforms/3d-rendering-context-behavior.html** failures are subject of test, but also blank page? * **/css/css-transforms/individual-transform/change-translate-property.html** * **/css/css-transforms/preserve-3d-flat-grouping-properties.html** * **/css/css-transforms/transforms-support-calc.html** * **/css/css-transitions/inherit-height-transition.html** * **/css/css-ui/inheritance.html** * **/css/css-ui/parsing/outline-width-computed.html** failures are subject of test; https://drafts.csswg.org/css-values-4/#snap-a-length-as-a-border-width * **/css/css-values/lh-unit-003.html** * **/css/css-values/viewport-units-compute.html** * **/css/css-values/viewport-units-keyframes.html** * **/css/css-values/viewport-units-media-queries.html** * **/css/css-values/viewport-units-writing-mode.html** * **/css/cssom-view/elementsFromPoint-table.html** * **/css/cssom-view/scroll-behavior-default-css.html** * **/css/cssom-view/scroll-behavior-element.html** * **/css/cssom-view/scroll-behavior-main-frame-root.html** * **/css/cssom-view/scroll-behavior-main-frame-window.html** * **/css/cssom-view/scroll-behavior-smooth-navigation.html** * **/css/cssom-view/scroll-behavior-subframe-root.html** * **/css/cssom/computed-style-003.html** * **/css/cssom/computed-style-004.html** * **/css/cssom/font-variant-shorthand-serialization.html** * **/css/selectors/dir-selector-auto.html** * **/css/selectors/has-argument-with-explicit-scope.html** * **/css/selectors/has-basic.html** * **/css/selectors/has-relative-argument.html** * **/css/selectors/invalidation/attribute-or-elemental-selectors-in-has.html** * **/css/selectors/invalidation/child-indexed-pseudo-classes-in-has.html** * **/css/selectors/invalidation/dir-pseudo-class-in-has.html** * **/css/selectors/invalidation/empty-pseudo-in-has.html** * **/css/selectors/invalidation/has-in-adjacent-position.html** * **/css/selectors/invalidation/has-in-ancestor-position.html** * **/css/selectors/invalidation/has-in-parent-position.html** * **/css/selectors/invalidation/has-in-sibling-position.html** * **/css/selectors/invalidation/has-invalidation-after-removing-non-first-element.html** * **/css/selectors/invalidation/has-invalidation-for-wiping-an-element.html** * **/css/selectors/invalidation/has-sibling.html** * **/css/selectors/invalidation/has-with-not.html** * **/css/selectors/invalidation/has-with-pseudo-class.html** * **/css/selectors/invalidation/input-pseudo-classes-in-has.html** * **/css/selectors/invalidation/is-pseudo-containing-complex-in-has.html** * **/css/selectors/invalidation/lang-pseudo-class-in-has.html** * **/css/selectors/invalidation/not-pseudo-containing-complex-in-has.html** * **/css/selectors/invalidation/typed-child-indexed-pseudo-classes-in-has.html** * **/css/selectors/is-where-basic.html** * **/css/selectors/is-where-not.html** * **/html/rendering/non-replaced-elements/tables/form-in-tables.html** * /html/rendering/replaced-elements/embedded-content-rendering-rules/canvas-update- * **/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-attribute-changes.html** * **/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-normal-descendant-change.html** * **/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-remove.html** * **/html/semantics/embedded-content/the-img-element/image-loading-lazy-slow-aspect-ratio.html** * **/html/semantics/embedded-content/the-img-element/image-loading-lazy-slow.html** * **/html/semantics/interactive-elements/the-dialog-element/inertness-with-modal-dialogs-and-iframes.html** * **/html/semantics/popovers/popover-stacking.html** * **/referrer-policy/generic/inheritance/popup-inheritance-form-submission.html** * **/resource-timing/resource-reload-TAO.html** * **/selection/bidi/modify.tentative.html** * **/selection/contenteditable/modify.tentative.html** * **/selection/textcontrols/selectionchange.html** * **/css/CSS2/normal-flow/block-in-inline-client-rects-001.html** * **/css/CSS2/positioning/relpos-percentage-top-in-scrollable.html** * **/css/css-animations/computed-style-animation-parsing.html** * **/css/css-variables/variables-substitute-guaranteed-invalid.html** * **/css/cssom-view/elementsFromPoint-simple.html** * **/css/cssom/CSSStyleSheet-modify-after-removal.html** * **/css/cssom/getComputedStyle-display-none-001.html** * **/css/selectors/focus-visible-script-focus-001.html** * **/css/selectors/has-specificity.html** * **/css/selectors/invalidation/is.html** * **/css/selectors/invalidation/not-002.html** * **/dom/events/EventListener-handleEvent-cross-realm.html** * **/dom/traversal/TreeWalker-acceptNode-filter-cross-realm.html** * **/html/browsers/the-window-object/window-properties.https.html** * **/html/browsers/the-window-object/window-prototype-chain.html** * **/html/browsers/windows/nested-browsing-contexts/frameElement.sub.html** * **/html/dom/aria-element-reflection.html** * **/html/rendering/replaced-elements/embedded-content-rendering-rules/canvas-update-with-border-object-fit.html** * **/html/semantics/forms/form-submission-0/form-double-submit-multiple-targets.html** * **/html/semantics/forms/the-input-element/show-picker-cross-origin-iframe.html** * **/html/webappapis/scripting/events/compile-event-handler-lexical-scopes-form-owner.html** * **/quirks/unitless-length/excluded-properties-002.html** </details> <details><summary>22× tests with failures that looked interesting</summary> * 1× CRASH [expected ...] * **/css/css-fonts/crash-large-grapheme-cluster.html** crash is subject of test * 6× FAIL [expected PASS] /... (reftest) * **/css/css-flexbox/anonymous-flex-item-005.html** old pass was spurious * **/css/css-flexbox/anonymous-flex-item-006.html** old pass was spurious * **/css/css-text-decor/text-decoration-line-recalc.html** old pass was spurious; ‘text-decoration’ shorthand unimplemented * **/css/css-ui/appearance-auto-non-html-namespace-001.html** old pass was spurious * **/html/canvas/element/drawing-text-to-the-canvas/direction-inherit-rtl.html** old pass was spurious * **/html/canvas/element/drawing-text-to-the-canvas/direction-rtl.html** old pass was spurious * 13× TIMEOUT [expected ...] * **/css/css-fonts/font-size-monospace-adjust.html** timeout is subject of test; reftest runner bug with 1e10s transition? * **/css/cssom-view/background-change-during-smooth-scroll.html** timeout is subject of test * **/css/selectors/invalidation/has-complexity.html** timeout is subject of test * **/css/selectors/invalidation/media-loading-pseudo-classes-in-has.html** timeout is subject of test; :has() unimplemented * **/fetch/stale-while-revalidate/stale-image.html** timeout is subject of test * **/html/browsers/browsing-the-web/history-traversal/history-traversal-navigates-multiple-frames.html** timeout is subject of test * **/html/rendering/widgets/appearance/appearance-animation-001.html** timeout is subject of test; reftest runner bug with 1e10s animation? * **/html/rendering/widgets/appearance/appearance-animation-002.html** timeout is subject of test; reftest runner bug with 1e10s animation? * **/html/rendering/widgets/appearance/appearance-transition-001.html** timeout is subject of test; reftest runner bug with 1e10s transition? * **/html/rendering/widgets/appearance/appearance-transition-002.html** timeout is subject of test; reftest runner bug with 1e10s transition? * **/html/rendering/widgets/appearance/appearance-transition-003.html** timeout is subject of test; reftest runner bug with 1e10s transition? * **/resource-timing/opaque-origin.html** timeout is subject of test * **/selection/textcontrols/selectionchange-bubble.html** timeout is subject of test * **/webidl/ecmascript-binding/invalid-this-value-cross-realm.html** ‘HTMLDocument’ unimplemented </details> ---  - [x] `./mach build -d` does not report any errors - [x] `./mach test-tidy` does not report any errors - [x] These changes fix #27949 (GitHub issue number if applicable)  - [x] There are tests for these changes (including but not limited to web-platform-tests/wpt#39211) OR - [ ] These changes do not require tests because ___
2025-08-06 14:10:11 +01:00 · 2023-03-28 18:31:41 +02:00 · 2023-03-28 18:31:41 +02:00 · e0f87cbba2
commit e0f87cbba2
parent edbd1dbc2c d3f1309310
267 changed files with 6147 additions and 1467 deletions
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@ -3290,6 +3290,13 @@ rooted!(in(*cx) let mut prototype_proto = ptr::null_mut::<JSObject>());
 %s;
 assert!(!prototype_proto.is_null());""" % getPrototypeProto)]

+        if self.descriptor.hasNamedPropertiesObject():
+            assert not self.haveUnscopables
+            code.append(CGGeneric("""\
+rooted!(in(*cx) let mut prototype_proto_proto = prototype_proto.get());
+dom::types::%s::create_named_properties_object(cx, prototype_proto_proto.handle(), prototype_proto.handle_mut());
+assert!(!prototype_proto.is_null());""" % name))
+
        properties = {
            "id": name,
            "unscopables": "unscopable_names" if self.haveUnscopables else "&[]",
@ -5508,15 +5515,15 @@ class CGDOMJSProxyHandler_getOwnPropertyDescriptor(CGAbstractExternMethod):
                attrs += " | JSPROP_READONLY"
            fillDescriptor = ("set_property_descriptor(\n"
                              "    MutableHandle::from_raw(desc),\n"
-                              "    result_root.handle(),\n"
+                              "    rval.handle(),\n"
                              "    (%s) as u32,\n"
                              "    &mut *is_none\n"
                              ");\n"
                              "return true;" % attrs)
            templateValues = {
-                'jsvalRef': 'result_root.handle_mut()',
+                'jsvalRef': 'rval.handle_mut()',
                'successCode': fillDescriptor,
-                'pre': 'rooted!(in(*cx) let mut result_root = UndefinedValue());'
+                'pre': 'rooted!(in(*cx) let mut rval = UndefinedValue());'
            }
            get += ("if let Some(index) = index {\n"
                    + "    let this = UnwrapProxy(proxy);\n"
@ -5524,8 +5531,7 @@ class CGDOMJSProxyHandler_getOwnPropertyDescriptor(CGAbstractExternMethod):
                    + CGIndenter(CGProxyIndexedGetter(self.descriptor, templateValues)).define() + "\n"
                    + "}\n")

-        namedGetter = self.descriptor.operations['NamedGetter']
-        if namedGetter:
+        if self.descriptor.supportsNamedProperties():
            attrs = []
            if not self.descriptor.interface.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
                attrs.append("JSPROP_ENUMERATE")
@ -5537,15 +5543,15 @@ class CGDOMJSProxyHandler_getOwnPropertyDescriptor(CGAbstractExternMethod):
                attrs = "0"
            fillDescriptor = ("set_property_descriptor(\n"
                              "    MutableHandle::from_raw(desc),\n"
-                              "    result_root.handle(),\n"
+                              "    rval.handle(),\n"
                              "    (%s) as u32,\n"
                              "    &mut *is_none\n"
                              ");\n"
                              "return true;" % attrs)
            templateValues = {
-                'jsvalRef': 'result_root.handle_mut()',
+                'jsvalRef': 'rval.handle_mut()',
                'successCode': fillDescriptor,
-                'pre': 'rooted!(in(*cx) let mut result_root = UndefinedValue());'
+                'pre': 'rooted!(in(*cx) let mut rval = UndefinedValue());'
            }

            # See the similar-looking in CGDOMJSProxyHandler_get for the spec quote.
@ -5638,7 +5644,7 @@ class CGDOMJSProxyHandler_defineProperty(CGAbstractExternMethod):
                    + CGIndenter(CGProxyNamedSetter(self.descriptor)).define()
                    + "    return (*opresult).succeed();\n"
                    + "}\n")
-        elif self.descriptor.operations['NamedGetter']:
+        elif self.descriptor.supportsNamedProperties():
            set += ("if id.is_string() || id.is_int() {\n"
                    + CGIndenter(CGProxyNamedGetter(self.descriptor)).define()
                    + "    if result.is_some() {\n"
@ -5722,7 +5728,7 @@ class CGDOMJSProxyHandler_ownPropertyKeys(CGAbstractExternMethod):
                }
                """)

-        if self.descriptor.operations['NamedGetter']:
+        if self.descriptor.supportsNamedProperties():
            body += dedent(
                """
                for name in (*unwrapped_proxy).SupportedPropertyNames() {
@ -5844,11 +5850,10 @@ class CGDOMJSProxyHandler_hasOwn(CGAbstractExternMethod):
                        + "    return true;\n"
                        + "}\n\n")

-        namedGetter = self.descriptor.operations['NamedGetter']
        condition = "id.is_string() || id.is_int()"
        if indexedGetter:
            condition = "index.is_none() && (%s)" % condition
-        if namedGetter:
+        if self.descriptor.supportsNamedProperties():
            named = """\
 if %s {
    let mut has_on_proto = false;
@ -5943,8 +5948,7 @@ if !expando.is_null() {
        else:
            getIndexedOrExpando = getFromExpando + "\n"

-        namedGetter = self.descriptor.operations['NamedGetter']
-        if namedGetter:
+        if self.descriptor.supportsNamedProperties():
            condition = "id.is_string() || id.is_int()"
            # From step 1:
            #     If O supports indexed properties and P is an array index, then:
@ -6214,7 +6218,7 @@ class CGInterfaceTrait(CGThing):
                               ),
                               rettype)

-            if descriptor.proxy:
+            if descriptor.proxy or descriptor.isGlobal():
                for name, operation in descriptor.operations.items():
                    if not operation or operation.isStringifier():
                        continue
--- a/components/script/dom/bindings/codegen/Configuration.py
+++ b/components/script/dom/bindings/codegen/Configuration.py
@ -280,7 +280,8 @@ class Descriptor(DescriptorProvider):
                        continue

                    def addIndexedOrNamedOperation(operation, m):
-                        self.proxy = True
+                        if not self.isGlobal():
+                            self.proxy = True
                        if m.isIndexed():
                            operation = 'Indexed' + operation
                        else:
@ -369,6 +370,15 @@ class Descriptor(DescriptorProvider):
    def internalNameFor(self, name):
        return self._internalNames.get(name, name)

+    def hasNamedPropertiesObject(self):
+        if self.interface.isExternal():
+            return False
+
+        return self.isGlobal() and self.supportsNamedProperties()
+
+    def supportsNamedProperties(self):
+        return self.operations['NamedGetter'] is not None
+
    def getExtendedAttributes(self, member, getter=False, setter=False):
        def maybeAppendInfallibleToAttrs(attrs, throws):
            if throws is None:
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@ -464,12 +464,6 @@ impl CollectionFilter for AnchorsFilter {
    }
 }

-enum ElementLookupResult {
-    None,
-    One(DomRoot<Element>),
-    Many,
-}
-
 #[allow(non_snake_case)]
 impl Document {
    pub fn note_node_with_dirty_descendants(&self, node: &Node) {
@ -2870,73 +2864,12 @@ impl Document {
            .for_each(|(_, context)| context.send_swap_chain_present());
    }

-    // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:supported-property-names
-    // (This takes the filter as a method so the window named getter can use it too)
-    pub fn supported_property_names_impl(
-        &self,
-        nameditem_filter: fn(&Node, &Atom) -> bool,
-    ) -> Vec<DOMString> {
-        // The tricky part here is making sure we return the names in
-        // tree order, without just resorting to a full tree walkthrough.
+    pub fn id_map(&self) -> Ref<HashMap<Atom, Vec<Dom<Element>>>> {
+        self.id_map.borrow()
+    }

-        let mut first_elements_with_name: HashMap<&Atom, &Dom<Element>> = HashMap::new();
-
-        // Get the first-in-tree-order element for each name in the name_map
-        let name_map = self.name_map.borrow();
-        name_map.iter().for_each(|(name, value)| {
-            if let Some(first) = value
-                .iter()
-                .find(|n| nameditem_filter((***n).upcast::<Node>(), &name))
-            {
-                first_elements_with_name.insert(name, first);
-            }
-        });
-
-        // Get the first-in-tree-order element for each name in the id_map;
-        // if we already had one from the name_map, figure out which of
-        // the two is first.
-        let id_map = self.id_map.borrow();
-        id_map.iter().for_each(|(name, value)| {
-            if let Some(first) = value
-                .iter()
-                .find(|n| nameditem_filter((***n).upcast::<Node>(), &name))
-            {
-                match first_elements_with_name.get(&name) {
-                    None => {
-                        first_elements_with_name.insert(name, first);
-                    },
-                    Some(el) => {
-                        if *el != first && first.upcast::<Node>().is_before(el.upcast::<Node>()) {
-                            first_elements_with_name.insert(name, first);
-                        }
-                    },
-                }
-            }
-        });
-
-        // first_elements_with_name now has our supported property names
-        // as keys, and the elements to order on as values.
-        let mut sortable_vec: Vec<(&Atom, &Dom<Element>)> = first_elements_with_name
-            .iter()
-            .map(|(k, v)| (*k, *v))
-            .collect();
-        sortable_vec.sort_unstable_by(|a, b| {
-            if a.1 == b.1 {
-                // This can happen if an img has an id different from its name,
-                // spec does not say which string to put first.
-                a.0.cmp(&b.0)
-            } else if a.1.upcast::<Node>().is_before(b.1.upcast::<Node>()) {
-                Ordering::Less
-            } else {
-                Ordering::Greater
-            }
-        });
-
-        // And now that they're sorted, we can return the keys
-        sortable_vec
-            .iter()
-            .map(|(k, _v)| DOMString::from(&***k))
-            .collect()
+    pub fn name_map(&self) -> Ref<HashMap<Atom, Vec<Dom<Element>>>> {
+        self.name_map.borrow()
    }
 }

@ -3869,79 +3802,16 @@ impl Document {
        )
    }

-    // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:determine-the-value-of-a-named-property
-    // Support method for steps 1-3:
-    // Count if there are 0, 1, or >1 elements that match the name.
-    // (This takes the filter as a method so the window named getter can use it too)
-    fn look_up_named_elements(
-        &self,
-        name: &Atom,
-        nameditem_filter: fn(&Node, &Atom) -> bool,
-    ) -> ElementLookupResult {
-        // We might match because of either id==name or name==name, so there
-        // are two sets of nodes to look through, but we don't need a
-        // full tree traversal.
-        let id_map = self.id_map.borrow();
-        let name_map = self.name_map.borrow();
-        let id_vec = id_map.get(&name);
-        let name_vec = name_map.get(&name);
+    pub fn get_elements_with_id(&self, id: &Atom) -> Ref<[Dom<Element>]> {
+        Ref::map(self.id_map.borrow(), |map| {
+            map.get(id).map(|vec| &**vec).unwrap_or_default()
+        })
+    }

-        // If nothing can possibly have the name, exit fast
-        if id_vec.is_none() && name_vec.is_none() {
-            return ElementLookupResult::None;
-        }
-
-        let one_from_id_map = if let Some(id_vec) = id_vec {
-            let mut elements = id_vec
-                .iter()
-                .filter(|n| nameditem_filter((***n).upcast::<Node>(), &name))
-                .peekable();
-            if let Some(first) = elements.next() {
-                if elements.peek().is_none() {
-                    Some(first)
-                } else {
-                    return ElementLookupResult::Many;
-                }
-            } else {
-                None
-            }
-        } else {
-            None
-        };
-
-        let one_from_name_map = if let Some(name_vec) = name_vec {
-            let mut elements = name_vec
-                .iter()
-                .filter(|n| nameditem_filter((***n).upcast::<Node>(), &name))
-                .peekable();
-            if let Some(first) = elements.next() {
-                if elements.peek().is_none() {
-                    Some(first)
-                } else {
-                    return ElementLookupResult::Many;
-                }
-            } else {
-                None
-            }
-        } else {
-            None
-        };
-
-        // We now have two elements, or one element, or the same
-        // element twice, or no elements.
-        match (one_from_id_map, one_from_name_map) {
-            (Some(one), None) | (None, Some(one)) => {
-                ElementLookupResult::One(DomRoot::from_ref(&one))
-            },
-            (Some(one), Some(other)) => {
-                if one == other {
-                    ElementLookupResult::One(DomRoot::from_ref(&one))
-                } else {
-                    ElementLookupResult::Many
-                }
-            },
-            (None, None) => ElementLookupResult::None,
-        }
+    pub fn get_elements_with_name(&self, name: &Atom) -> Ref<[Dom<Element>]> {
+        Ref::map(self.name_map.borrow(), |map| {
+            map.get(name).map(|vec| &**vec).unwrap_or_default()
+        })
    }

    #[allow(unrooted_must_root)]
@ -4871,45 +4741,76 @@ impl DocumentMethods for Document {
    #[allow(unsafe_code)]
    // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:dom-document-nameditem-filter
    fn NamedGetter(&self, _cx: JSContext, name: DOMString) -> Option<NonNull<JSObject>> {
-        #[derive(JSTraceable, MallocSizeOf)]
-        struct NamedElementFilter {
-            name: Atom,
+        if name.is_empty() {
+            return None;
        }
-        impl CollectionFilter for NamedElementFilter {
-            fn filter(&self, elem: &Element, _root: &Node) -> bool {
-                elem.upcast::<Node>().is_document_named_item(&self.name)
+        let name = Atom::from(name);
+
+        // Step 1.
+        let elements_with_name = self.get_elements_with_name(&name);
+        let name_iter = elements_with_name
+            .iter()
+            .filter(|elem| is_named_element_with_name_attribute(elem));
+        let elements_with_id = self.get_elements_with_id(&name);
+        let id_iter = elements_with_id
+            .iter()
+            .filter(|elem| is_named_element_with_id_attribute(elem));
+        let mut elements = name_iter.chain(id_iter);
+
+        let first = elements.next()?;
+
+        if elements.next().is_none() {
+            // Step 2.
+            if let Some(nested_window_proxy) = first
+                .downcast::<HTMLIFrameElement>()
+                .and_then(|iframe| iframe.GetContentWindow())
+            {
+                unsafe {
+                    return Some(NonNull::new_unchecked(
+                        nested_window_proxy.reflector().get_jsobject().get(),
+                    ));
+                }
+            }
+
+            // Step 3.
+            unsafe {
+                return Some(NonNull::new_unchecked(
+                    first.reflector().get_jsobject().get(),
+                ));
            }
        }

-        let name = Atom::from(name);
-
-        match self.look_up_named_elements(&name, Node::is_document_named_item) {
-            ElementLookupResult::None => {
-                return None;
-            },
-            ElementLookupResult::One(element) => {
-                if let Some(nested_proxy) = element
-                    .downcast::<HTMLIFrameElement>()
-                    .and_then(|iframe| iframe.GetContentWindow())
-                {
-                    unsafe {
-                        return Some(NonNull::new_unchecked(
-                            nested_proxy.reflector().get_jsobject().get(),
-                        ));
-                    }
-                }
-                unsafe {
-                    return Some(NonNull::new_unchecked(
-                        element.reflector().get_jsobject().get(),
-                    ));
-                }
-            },
-            ElementLookupResult::Many => {},
-        };
-
        // Step 4.
-        let filter = NamedElementFilter { name: name };
-        let collection = HTMLCollection::create(self.window(), self.upcast(), Box::new(filter));
+        #[derive(JSTraceable, MallocSizeOf)]
+        struct DocumentNamedGetter {
+            name: Atom,
+        }
+        impl CollectionFilter for DocumentNamedGetter {
+            fn filter(&self, elem: &Element, _root: &Node) -> bool {
+                let type_ = match elem.upcast::<Node>().type_id() {
+                    NodeTypeId::Element(ElementTypeId::HTMLElement(type_)) => type_,
+                    _ => return false,
+                };
+                match type_ {
+                    HTMLElementTypeId::HTMLFormElement | HTMLElementTypeId::HTMLIFrameElement => {
+                        elem.get_name().as_ref() == Some(&self.name)
+                    },
+                    HTMLElementTypeId::HTMLImageElement => elem.get_name().map_or(false, |name| {
+                        name == *self.name ||
+                            !name.is_empty() && elem.get_id().as_ref() == Some(&self.name)
+                    }),
+                    // TODO handle <embed> and <object>; these depend on whether the element is
+                    // “exposed”, a concept that doesn’t fully make sense until embed/object
+                    // behaviour is actually implemented
+                    _ => false,
+                }
+            }
+        }
+        let collection = HTMLCollection::create(
+            self.window(),
+            self.upcast(),
+            Box::new(DocumentNamedGetter { name }),
+        );
        unsafe {
            Some(NonNull::new_unchecked(
                collection.reflector().get_jsobject().get(),
@ -4919,7 +4820,61 @@ impl DocumentMethods for Document {

    // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:supported-property-names
    fn SupportedPropertyNames(&self) -> Vec<DOMString> {
-        self.supported_property_names_impl(Node::is_document_named_item)
+        let mut names_with_first_named_element_map: HashMap<&Atom, &Element> = HashMap::new();
+
+        let name_map = self.name_map.borrow();
+        for (name, elements) in &*name_map {
+            if name.is_empty() {
+                continue;
+            }
+            let mut name_iter = elements
+                .iter()
+                .filter(|elem| is_named_element_with_name_attribute(elem));
+            if let Some(first) = name_iter.next() {
+                names_with_first_named_element_map.insert(name, first);
+            }
+        }
+        let id_map = self.id_map.borrow();
+        for (id, elements) in &*id_map {
+            if id.is_empty() {
+                continue;
+            }
+            let mut id_iter = elements
+                .iter()
+                .filter(|elem| is_named_element_with_id_attribute(elem));
+            if let Some(first) = id_iter.next() {
+                match names_with_first_named_element_map.entry(id) {
+                    Vacant(entry) => drop(entry.insert(first)),
+                    Occupied(mut entry) => {
+                        if first.upcast::<Node>().is_before(entry.get().upcast()) {
+                            *entry.get_mut() = first;
+                        }
+                    },
+                }
+            }
+        }
+
+        let mut names_with_first_named_element_vec: Vec<(&Atom, &Element)> =
+            names_with_first_named_element_map
+                .iter()
+                .map(|(k, v)| (*k, *v))
+                .collect();
+        names_with_first_named_element_vec.sort_unstable_by(|a, b| {
+            if a.1 == b.1 {
+                // This can happen if an img has an id different from its name,
+                // spec does not say which string to put first.
+                a.0.cmp(&b.0)
+            } else if a.1.upcast::<Node>().is_before(b.1.upcast::<Node>()) {
+                Ordering::Less
+            } else {
+                Ordering::Greater
+            }
+        });
+
+        names_with_first_named_element_vec
+            .iter()
+            .map(|(k, _v)| DOMString::from(&***k))
+            .collect()
    }

    // https://html.spec.whatwg.org/multipage/#dom-document-clear
@ -5394,3 +5349,26 @@ pub enum ReflowTriggerCondition {
    PendingRestyles,
    PaintPostponed,
 }
+
+fn is_named_element_with_name_attribute(elem: &Element) -> bool {
+    let type_ = match elem.upcast::<Node>().type_id() {
+        NodeTypeId::Element(ElementTypeId::HTMLElement(type_)) => type_,
+        _ => return false,
+    };
+    match type_ {
+        HTMLElementTypeId::HTMLFormElement |
+        HTMLElementTypeId::HTMLIFrameElement |
+        HTMLElementTypeId::HTMLImageElement => true,
+        // TODO handle <embed> and <object>; these depend on whether the element is
+        // “exposed”, a concept that doesn’t fully make sense until embed/object
+        // behaviour is actually implemented
+        _ => false,
+    }
+}
+
+fn is_named_element_with_id_attribute(elem: &Element) -> bool {
+    // TODO handle <embed> and <object>; these depend on whether the element is
+    // “exposed”, a concept that doesn’t fully make sense until embed/object
+    // behaviour is actually implemented
+    elem.is::<HTMLImageElement>() && elem.get_name().map_or(false, |name| !name.is_empty())
+}
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@ -82,7 +82,6 @@ use script_traits::UntrustedNodeAddress;
 use selectors::matching::{matches_selector_list, MatchingContext, MatchingMode};
 use selectors::parser::SelectorList;
 use servo_arc::Arc;
-use servo_atoms::Atom;
 use servo_url::ServoUrl;
 use smallvec::SmallVec;
 use std::borrow::Cow;
@ -1242,34 +1241,6 @@ impl Node {
        }
    }

-    // https://html.spec.whatwg.org/multipage/#dom-document-nameditem-filter
-    pub fn is_document_named_item(&self, name: &Atom) -> bool {
-        let html_elem_type = match self.type_id() {
-            NodeTypeId::Element(ElementTypeId::HTMLElement(type_)) => type_,
-            _ => return false,
-        };
-        let elem = self
-            .downcast::<Element>()
-            .expect("Node with an Element::HTMLElement NodeTypeID must be an Element");
-        match html_elem_type {
-            HTMLElementTypeId::HTMLFormElement | HTMLElementTypeId::HTMLIFrameElement => {
-                elem.get_name().map_or(false, |n| n == *name)
-            },
-            HTMLElementTypeId::HTMLImageElement =>
-            // Images can match by id, but only when their name is non-empty.
-            {
-                elem.get_name().map_or(false, |n| {
-                    n == *name || elem.get_id().map_or(false, |i| i == *name)
-                })
-            },
-            // TODO: Handle <embed> and <object>; these depend on
-            // whether the element is "exposed", a concept which
-            // doesn't fully make sense until embed/object behaviors
-            // are actually implemented.
-            _ => false,
-        }
-    }
-
    pub fn is_styled(&self) -> bool {
        self.style_and_layout_data.borrow().is_some()
    }
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@ -45,8 +45,7 @@
                             optional DOMString features = "");
  //getter WindowProxy (unsigned long index);

-  // https://github.com/servo/servo/issues/14453
-  // getter object (DOMString name);
+  getter object (DOMString name);

  // the user agent
  readonly attribute Navigator navigator;
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@ -6,6 +6,7 @@ use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::DocumentBinding::{
    DocumentMethods, DocumentReadyState,
 };
+use crate::dom::bindings::codegen::Bindings::HTMLIFrameElementBinding::HTMLIFrameElementMethods;
 use crate::dom::bindings::codegen::Bindings::HistoryBinding::HistoryBinding::HistoryMethods;
 use crate::dom::bindings::codegen::Bindings::ImageBitmapBinding::{
    ImageBitmapOptions, ImageBitmapSource,
@ -19,7 +20,7 @@ use crate::dom::bindings::codegen::Bindings::WindowBinding::{
 use crate::dom::bindings::codegen::Bindings::WindowBinding::{ScrollBehavior, ScrollToOptions};
 use crate::dom::bindings::codegen::UnionTypes::{RequestOrUSVString, StringOrFunction};
 use crate::dom::bindings::error::{Error, ErrorResult, Fallible};
-use crate::dom::bindings::inheritance::Castable;
+use crate::dom::bindings::inheritance::{Castable, ElementTypeId, HTMLElementTypeId, NodeTypeId};
 use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::DomObject;
@ -40,6 +41,8 @@ use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::hashchangeevent::HashChangeEvent;
 use crate::dom::history::History;
+use crate::dom::htmlcollection::{CollectionFilter, HTMLCollection};
+use crate::dom::htmliframeelement::HTMLIFrameElement;
 use crate::dom::identityhub::Identities;
 use crate::dom::location::Location;
 use crate::dom::mediaquerylist::{MediaQueryList, MediaQueryListMatchState};
@ -71,6 +74,7 @@ use crate::task_manager::TaskManager;
 use crate::task_source::{TaskSource, TaskSourceName};
 use crate::timers::{IsInterval, TimerCallback};
 use crate::webdriver_handlers::jsval_to_webdriver;
+use crate::window_named_properties;
 use app_units::Au;
 use backtrace::Backtrace;
 use base64;
@ -94,7 +98,9 @@ use js::jsapi::{GCReason, StackFormat, JS_GC};
 use js::jsval::UndefinedValue;
 use js::jsval::{JSVal, NullValue};
 use js::rust::wrappers::JS_DefineProperty;
-use js::rust::{CustomAutoRooter, CustomAutoRooterGuard, HandleValue};
+use js::rust::{
+    CustomAutoRooter, CustomAutoRooterGuard, HandleObject, HandleValue, MutableHandleObject,
+};
 use media::WindowGLContext;
 use msg::constellation_msg::{BrowsingContextId, PipelineId};
 use net_traits::image_cache::{ImageCache, ImageResponder, ImageResponse};
@ -120,17 +126,20 @@ use script_traits::{
 use script_traits::{TimerSchedulerMsg, WebrenderIpcSender, WindowSizeData, WindowSizeType};
 use selectors::attr::CaseSensitivity;
 use servo_arc::Arc as ServoArc;
+use servo_atoms::Atom;
 use servo_geometry::{f32_rect_to_au_rect, MaxRect};
 use servo_url::{ImmutableOrigin, MutableOrigin, ServoUrl};
 use std::borrow::Cow;
 use std::borrow::ToOwned;
 use std::cell::Cell;
+use std::cmp;
 use std::collections::hash_map::Entry;
 use std::collections::{HashMap, HashSet};
 use std::default::Default;
 use std::env;
 use std::io::{stderr, stdout, Write};
 use std::mem;
+use std::ptr::NonNull;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
@ -1386,9 +1395,179 @@ impl WindowMethods for Window {
    fn IsSecureContext(&self) -> bool {
        self.upcast::<GlobalScope>().is_secure_context()
    }
+
+    // https://html.spec.whatwg.org/multipage/#named-access-on-the-window-object
+    #[allow(unsafe_code)]
+    fn NamedGetter(&self, _cx: JSContext, name: DOMString) -> Option<NonNull<JSObject>> {
+        if name.is_empty() {
+            return None;
+        }
+        let document = self.Document();
+
+        // https://html.spec.whatwg.org/multipage/#document-tree-child-browsing-context-name-property-set
+        let iframes: Vec<_> = document
+            .iter_iframes()
+            .filter(|iframe| {
+                if let Some(window) = iframe.GetContentWindow() {
+                    return window.get_name() == name;
+                }
+                false
+            })
+            .collect();
+
+        let iframe_iter = iframes.iter().map(|iframe| iframe.upcast::<Element>());
+
+        let name = Atom::from(&*name);
+
+        // Step 1.
+        let elements_with_name = document.get_elements_with_name(&name);
+        let name_iter = elements_with_name
+            .iter()
+            .map(|element| &**element)
+            .filter(|elem| is_named_element_with_name_attribute(elem));
+        let elements_with_id = document.get_elements_with_id(&name);
+        let id_iter = elements_with_id
+            .iter()
+            .map(|element| &**element)
+            .filter(|elem| is_named_element_with_id_attribute(elem));
+
+        // Step 2.
+        for elem in iframe_iter.clone() {
+            if let Some(nested_window_proxy) = elem
+                .downcast::<HTMLIFrameElement>()
+                .and_then(|iframe| iframe.GetContentWindow())
+            {
+                unsafe {
+                    return Some(NonNull::new_unchecked(
+                        nested_window_proxy.reflector().get_jsobject().get(),
+                    ));
+                }
+            }
+        }
+
+        let mut elements = iframe_iter.chain(name_iter).chain(id_iter);
+
+        let first = elements.next()?;
+
+        if elements.next().is_none() {
+            // Step 3.
+            unsafe {
+                return Some(NonNull::new_unchecked(
+                    first.reflector().get_jsobject().get(),
+                ));
+            }
+        }
+
+        // Step 4.
+        #[derive(JSTraceable, MallocSizeOf)]
+        struct WindowNamedGetter {
+            name: Atom,
+        }
+        impl CollectionFilter for WindowNamedGetter {
+            fn filter(&self, elem: &Element, _root: &Node) -> bool {
+                let type_ = match elem.upcast::<Node>().type_id() {
+                    NodeTypeId::Element(ElementTypeId::HTMLElement(type_)) => type_,
+                    _ => return false,
+                };
+                if elem.get_id().as_ref() == Some(&self.name) {
+                    return true;
+                }
+                match type_ {
+                    HTMLElementTypeId::HTMLEmbedElement |
+                    HTMLElementTypeId::HTMLFormElement |
+                    HTMLElementTypeId::HTMLImageElement |
+                    HTMLElementTypeId::HTMLObjectElement => {
+                        elem.get_name().as_ref() == Some(&self.name)
+                    },
+                    _ => false,
+                }
+            }
+        }
+        let collection = HTMLCollection::create(
+            self,
+            document.upcast(),
+            Box::new(WindowNamedGetter { name }),
+        );
+        unsafe {
+            Some(NonNull::new_unchecked(
+                collection.reflector().get_jsobject().get(),
+            ))
+        }
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:supported-property-names
+    fn SupportedPropertyNames(&self) -> Vec<DOMString> {
+        let mut names_with_first_named_element_map: HashMap<&Atom, &Element> = HashMap::new();
+
+        let document = self.Document();
+        let name_map = document.name_map();
+        for (name, elements) in &*name_map {
+            if name.is_empty() {
+                continue;
+            }
+            let mut name_iter = elements
+                .iter()
+                .filter(|elem| is_named_element_with_name_attribute(elem));
+            if let Some(first) = name_iter.next() {
+                names_with_first_named_element_map.insert(name, first);
+            }
+        }
+        let id_map = document.id_map();
+        for (id, elements) in &*id_map {
+            if id.is_empty() {
+                continue;
+            }
+            let mut id_iter = elements
+                .iter()
+                .filter(|elem| is_named_element_with_id_attribute(elem));
+            if let Some(first) = id_iter.next() {
+                match names_with_first_named_element_map.entry(id) {
+                    Entry::Vacant(entry) => drop(entry.insert(first)),
+                    Entry::Occupied(mut entry) => {
+                        if first.upcast::<Node>().is_before(entry.get().upcast()) {
+                            *entry.get_mut() = first;
+                        }
+                    },
+                }
+            }
+        }
+
+        let mut names_with_first_named_element_vec: Vec<(&Atom, &Element)> =
+            names_with_first_named_element_map
+                .iter()
+                .map(|(k, v)| (*k, *v))
+                .collect();
+        names_with_first_named_element_vec.sort_unstable_by(|a, b| {
+            if a.1 == b.1 {
+                // This can happen if an img has an id different from its name,
+                // spec does not say which string to put first.
+                a.0.cmp(&b.0)
+            } else if a.1.upcast::<Node>().is_before(b.1.upcast::<Node>()) {
+                cmp::Ordering::Less
+            } else {
+                cmp::Ordering::Greater
+            }
+        });
+
+        names_with_first_named_element_vec
+            .iter()
+            .map(|(k, _v)| DOMString::from(&***k))
+            .collect()
+    }
 }

 impl Window {
+    // https://heycam.github.io/webidl/#named-properties-object
+    // https://html.spec.whatwg.org/multipage/#named-access-on-the-window-object
+    #[allow(unsafe_code)]
+    pub fn create_named_properties_object(
+        cx: JSContext,
+        proto: HandleObject,
+        object: MutableHandleObject,
+    ) {
+        window_named_properties::create(cx, proto, object)
+    }
+
    pub(crate) fn set_current_event(&self, event: Option<&Event>) -> Option<DomRoot<Event>> {
        let current = self
            .current_event
@ -2659,3 +2838,21 @@ impl ParseErrorReporter for CSSErrorReporter {
            ));
    }
 }
+
+fn is_named_element_with_name_attribute(elem: &Element) -> bool {
+    let type_ = match elem.upcast::<Node>().type_id() {
+        NodeTypeId::Element(ElementTypeId::HTMLElement(type_)) => type_,
+        _ => return false,
+    };
+    match type_ {
+        HTMLElementTypeId::HTMLEmbedElement |
+        HTMLElementTypeId::HTMLFormElement |
+        HTMLElementTypeId::HTMLImageElement |
+        HTMLElementTypeId::HTMLObjectElement => true,
+        _ => false,
+    }
+}
+
+fn is_named_element_with_id_attribute(elem: &Element) -> bool {
+    elem.is_html_element()
+}
--- a/components/script/dom/windowproxy.rs
+++ b/components/script/dom/windowproxy.rs
@ -910,7 +910,7 @@ unsafe extern "C" fn getOwnPropertyDescriptor(
        window.to_jsval(cx, val.handle_mut());
        set_property_descriptor(
            MutableHandle::from_raw(desc),
-            val.handle().into(),
+            val.handle(),
            attrs,
            &mut *is_none,
        );
--- a/components/script/lib.rs
+++ b/components/script/lib.rs
@ -110,6 +110,8 @@ mod timers;
 mod unpremultiplytable;
 #[warn(deprecated)]
 mod webdriver_handlers;
+#[warn(deprecated)]
+mod window_named_properties;

 pub use init::init;
 pub use script_runtime::JSEngineSetup;
--- a/components/script/window_named_properties.rs
+++ b/components/script/window_named_properties.rs
@ -0,0 +1,260 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
+use crate::dom::bindings::proxyhandler::set_property_descriptor;
+use crate::dom::bindings::root::Root;
+use crate::dom::bindings::utils::has_property_on_prototype;
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::window::Window;
+use crate::js::conversions::ToJSValConvertible;
+use crate::script_runtime::JSContext as SafeJSContext;
+use js::conversions::jsstr_to_string;
+use js::glue::{AppendToIdVector, CreateProxyHandler, NewProxyObject, ProxyTraps};
+use js::jsapi::{GetWellKnownSymbol, JS_SetImmutablePrototype, SymbolCode, JSPROP_READONLY};
+use js::jsapi::{
+    Handle, HandleObject, JSClass, JSContext, JSErrNum, MutableHandleObject, UndefinedHandleValue,
+};
+use js::jsapi::{
+    HandleId, JSClass_NON_NATIVE, MutableHandle, MutableHandleIdVector, ObjectOpResult,
+    PropertyDescriptor, ProxyClassExtension, ProxyClassOps, ProxyObjectOps,
+    JSCLASS_DELAY_METADATA_BUILDER, JSCLASS_IS_PROXY, JSCLASS_RESERVED_SLOTS_MASK,
+    JSCLASS_RESERVED_SLOTS_SHIFT,
+};
+use js::jsid::SymbolId;
+use js::jsval::UndefinedValue;
+use js::rust::IntoHandle;
+use js::rust::{Handle as RustHandle, MutableHandle as RustMutableHandle};
+use js::rust::{HandleObject as RustHandleObject, MutableHandleObject as RustMutableHandleObject};
+use libc;
+use std::ptr;
+
+struct SyncWrapper(*const libc::c_void);
+#[allow(unsafe_code)]
+unsafe impl Sync for SyncWrapper {}
+
+lazy_static! {
+    static ref HANDLER: SyncWrapper = {
+        let traps = ProxyTraps {
+            enter: None,
+            getOwnPropertyDescriptor: Some(get_own_property_descriptor),
+            defineProperty: Some(define_property),
+            ownPropertyKeys: Some(own_property_keys),
+            delete_: Some(delete),
+            enumerate: None,
+            getPrototypeIfOrdinary: Some(get_prototype_if_ordinary),
+            getPrototype: None,
+            setPrototype: None,
+            setImmutablePrototype: None,
+            preventExtensions: Some(prevent_extensions),
+            isExtensible: Some(is_extensible),
+            has: None,
+            get: None,
+            set: None,
+            call: None,
+            construct: None,
+            hasOwn: None,
+            getOwnEnumerablePropertyKeys: None,
+            nativeCall: None,
+            objectClassIs: None,
+            className: Some(class_name),
+            fun_toString: None,
+            boxedValue_unbox: None,
+            defaultValue: None,
+            trace: None,
+            finalize: None,
+            objectMoved: None,
+            isCallable: None,
+            isConstructor: None,
+        };
+
+        #[allow(unsafe_code)]
+        unsafe {
+            SyncWrapper(CreateProxyHandler(&traps, ptr::null()))
+        }
+    };
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn get_own_property_descriptor(
+    cx: *mut JSContext,
+    proxy: HandleObject,
+    id: HandleId,
+    desc: MutableHandle<PropertyDescriptor>,
+    is_none: *mut bool,
+) -> bool {
+    let cx = SafeJSContext::from_ptr(cx);
+
+    if id.is_symbol() {
+        if id.get().asBits_ == SymbolId(GetWellKnownSymbol(*cx, SymbolCode::toStringTag)).asBits_ {
+            rooted!(in(*cx) let mut rval = UndefinedValue());
+            "WindowProperties".to_jsval(*cx, rval.handle_mut());
+            set_property_descriptor(
+                RustMutableHandle::from_raw(desc),
+                rval.handle(),
+                JSPROP_READONLY.into(),
+                &mut *is_none,
+            );
+        }
+        return true;
+    }
+
+    let mut found = false;
+    if !has_property_on_prototype(
+        *cx,
+        RustHandle::from_raw(proxy),
+        RustHandle::from_raw(id),
+        &mut found,
+    ) {
+        return false;
+    }
+    if found {
+        return true;
+    }
+
+    let s = if id.is_string() {
+        jsstr_to_string(*cx, id.to_string())
+    } else if id.is_int() {
+        // If the property key is an integer index, convert it to a String too.
+        // For indexed access on the window object, which may shadow this, see
+        // the getOwnPropertyDescriptor trap in dom/windowproxy.rs.
+        id.to_int().to_string()
+    } else if id.is_symbol() {
+        // Symbol properties were already handled above.
+        unreachable!()
+    } else {
+        unimplemented!()
+    };
+    if s.is_empty() {
+        return true;
+    }
+
+    let window = Root::downcast::<Window>(GlobalScope::from_object(proxy.get()))
+        .expect("global is not a window");
+    if let Some(obj) = window.NamedGetter(cx, s.into()) {
+        rooted!(in(*cx) let mut rval = UndefinedValue());
+        obj.to_jsval(*cx, rval.handle_mut());
+        set_property_descriptor(
+            RustMutableHandle::from_raw(desc),
+            rval.handle(),
+            0,
+            &mut *is_none,
+        );
+    }
+    return true;
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn own_property_keys(
+    cx: *mut JSContext,
+    _proxy: HandleObject,
+    props: MutableHandleIdVector,
+) -> bool {
+    // TODO is this all we need to return? compare with gecko:
+    // https://searchfox.org/mozilla-central/rev/af78418c4b5f2c8721d1a06486cf4cf0b33e1e8d/dom/base/WindowNamedPropertiesHandler.cpp#175-232
+    // see also https://github.com/whatwg/html/issues/9068
+    rooted!(in(cx) let mut rooted = SymbolId(GetWellKnownSymbol(cx, SymbolCode::toStringTag)));
+    AppendToIdVector(props, rooted.handle().into());
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn define_property(
+    _cx: *mut JSContext,
+    _proxy: HandleObject,
+    _id: HandleId,
+    _desc: Handle<PropertyDescriptor>,
+    result: *mut ObjectOpResult,
+) -> bool {
+    (*result).code_ = JSErrNum::JSMSG_CANT_DEFINE_WINDOW_NAMED_PROPERTY as usize;
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn delete(
+    _cx: *mut JSContext,
+    _proxy: HandleObject,
+    _id: HandleId,
+    result: *mut ObjectOpResult,
+) -> bool {
+    (*result).code_ = JSErrNum::JSMSG_CANT_DELETE_WINDOW_NAMED_PROPERTY as usize;
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn get_prototype_if_ordinary(
+    _cx: *mut JSContext,
+    proxy: HandleObject,
+    is_ordinary: *mut bool,
+    proto: MutableHandleObject,
+) -> bool {
+    *is_ordinary = true;
+    proto.set(js::jsapi::GetStaticPrototype(proxy.get()));
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn prevent_extensions(
+    _cx: *mut JSContext,
+    _proxy: HandleObject,
+    result: *mut ObjectOpResult,
+) -> bool {
+    (*result).code_ = JSErrNum::JSMSG_CANT_PREVENT_EXTENSIONS as usize;
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn is_extensible(
+    _cx: *mut JSContext,
+    _proxy: HandleObject,
+    extensible: *mut bool,
+) -> bool {
+    *extensible = true;
+    true
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn class_name(_cx: *mut JSContext, _proxy: HandleObject) -> *const libc::c_char {
+    &b"WindowProperties\0" as *const _ as *const _
+}
+
+// Maybe this should be a DOMJSClass. See https://bugzilla.mozilla.org/show_bug.cgi?id=787070
+#[allow(unsafe_code)]
+static CLASS: JSClass = JSClass {
+    name: b"WindowProperties\0" as *const u8 as *const libc::c_char,
+    flags: JSClass_NON_NATIVE |
+        JSCLASS_IS_PROXY |
+        JSCLASS_DELAY_METADATA_BUILDER |
+        ((1 & JSCLASS_RESERVED_SLOTS_MASK) << JSCLASS_RESERVED_SLOTS_SHIFT), /* JSCLASS_HAS_RESERVED_SLOTS(1) */
+    cOps: unsafe { &ProxyClassOps },
+    spec: ptr::null(),
+    ext: unsafe { &ProxyClassExtension },
+    oOps: unsafe { &ProxyObjectOps },
+};
+
+#[allow(unsafe_code)]
+pub fn create(
+    cx: SafeJSContext,
+    proto: RustHandleObject,
+    mut properties_obj: RustMutableHandleObject,
+) {
+    unsafe {
+        properties_obj.set(NewProxyObject(
+            *cx,
+            HANDLER.0,
+            UndefinedHandleValue,
+            proto.get(),
+            &CLASS,
+            false,
+        ));
+        assert!(!properties_obj.get().is_null());
+        let mut succeeded = false;
+        assert!(JS_SetImmutablePrototype(
+            *cx,
+            properties_obj.handle().into_handle(),
+            &mut succeeded
+        ));
+        assert!(succeeded);
+    }
+}