Add onslotchange event handler IDL attribute

`onslotchange` IDL attribute is supported by interfaces:
- GlobalEventHandlers [1]
- ShadowRoot [2]

Reflects following spec changes:
- whatwg/html#4129
- whatwg/dom#785

Those new spec addition is already implemented in Safari and Gecko[3].

Intent to Ship mail with 3 approvals: [4]

[1] https://html.spec.whatwg.org/#globaleventhandlers
[2] https://dom.spec.whatwg.org/#interface-shadowroot
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=1501983
[4] https://groups.google.com/a/chromium.org/g/blink-dev/c/cagoIboJ6Oo/m/roPoRAEDBAAJ

R=fwang@igalia.com, rego@igalia.com

Bug: 1006096
Change-Id: I3d0d7eb437aba3e40d24cca9bcf31d1db701f970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3096889
Commit-Queue: SONIA SINGLA <ssingla@igalia.com>
Reviewed-by: Mason Freed <masonf@chromium.org>
Reviewed-by: Manuel Rego <rego@igalia.com>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#931541}
NOKEYCHECK=True
GitOrigin-RevId: ec5cf31361e9822ad4c8999dcb34aa1bcca2907a

blink/renderer/core/dom/global_event_handlers.h

@@ -112,6 +112,7 @@ class GlobalEventHandlers {
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(select, kSelect)
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(selectionchange, kSelectionchange)
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(selectstart, kSelectstart)
+  DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(slotchange, kSlotchange)
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(stalled, kStalled)
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(submit, kSubmit)
   DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(suspend, kSuspend)

blink/renderer/core/dom/global_event_handlers.idl

@@ -87,6 +87,7 @@
     attribute EventHandler onseeked;
     attribute EventHandler onseeking;
     attribute EventHandler onselect;
+    attribute EventHandler onslotchange;
     //attribute EventHandler onsort;
     attribute EventHandler onstalled;
     attribute EventHandler onsubmit;

blink/renderer/core/dom/shadow_root.h

@@ -66,6 +66,8 @@ class CORE_EXPORT ShadowRoot final : public DocumentFragment, public TreeScope {
   using TreeScope::SetDocument;
   using TreeScope::SetParentTreeScope;
 
+  DEFINE_ATTRIBUTE_EVENT_LISTENER(slotchange, kSlotchange)
+
   Element& host() const {
     DCHECK(ParentOrShadowHostNode());
     return *To<Element>(ParentOrShadowHostNode());

blink/renderer/core/dom/shadow_root.idl

@@ -30,6 +30,7 @@
 interface ShadowRoot : DocumentFragment {
     readonly attribute ShadowRootMode mode;
     readonly attribute Element host;
+    attribute EventHandler onslotchange;
     // TODO(lyf): Change the type to `[TreatNullAs=xxx] HTMLString` after
     // https://crbug.com/1058762 has been fixed.
     [CEReactions, RaisesException=Setter] attribute [TreatNullAs=EmptyString, StringContext=TrustedHTML] DOMString innerHTML;

blink/renderer/core/html/html_attribute_names.json5

@@ -249,6 +249,7 @@
     "onselectstart",
     "onselectionchange",
     "onshow",
+    "onslotchange",
     "onstalled",
     "onstorage",
     "onsuspend",

blink/renderer/core/html/html_element.cc

@@ -572,6 +572,8 @@ AttributeTriggers* HTMLElement::TriggersForAttributeName(
        nullptr},
       {html_names::kOnselectstartAttr, kNoWebFeature,
        event_type_names::kSelectstart, nullptr},
+      {html_names::kOnslotchangeAttr, kNoWebFeature,
+       event_type_names::kSlotchange, nullptr},
       {html_names::kOnstalledAttr, kNoWebFeature, event_type_names::kStalled,
        nullptr},
       {html_names::kOnsubmitAttr, kNoWebFeature, event_type_names::kSubmit,

blink/web_tests/external/wpt/dom/idlharness.window_exclude=Node-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 1286 tests; 1282 PASS, 4 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 1286 tests; 1283 PASS, 3 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS idl_test setup
 PASS idl_test validation
 PASS Partial interface Window: original interface defined
@@ -559,7 +559,7 @@ PASS ShadowRoot interface: attribute mode
 PASS ShadowRoot interface: attribute delegatesFocus
 PASS ShadowRoot interface: attribute slotAssignment
 PASS ShadowRoot interface: attribute host
-FAIL ShadowRoot interface: attribute onslotchange assert_true: The prototype object must have a property "onslotchange" expected true got false
+PASS ShadowRoot interface: attribute onslotchange
 PASS Element interface: existence and properties of interface object
 PASS Element interface object length
 PASS Element interface object name

blink/web_tests/external/wpt/html/dom/idlharness.https_exclude=(Document_Window_HTML._)-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 1459 tests; 1418 PASS, 41 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 1459 tests; 1419 PASS, 40 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS idl_test setup
 PASS idl_test validation
 PASS Partial interface Document: original interface defined
@@ -1420,7 +1420,7 @@ FAIL SVGElement interface: attribute onsecuritypolicyviolation assert_true: The
 PASS SVGElement interface: attribute onseeked
 PASS SVGElement interface: attribute onseeking
 PASS SVGElement interface: attribute onselect
-FAIL SVGElement interface: attribute onslotchange assert_true: The prototype object must have a property "onslotchange" expected true got false
+PASS SVGElement interface: attribute onslotchange
 PASS SVGElement interface: attribute onstalled
 PASS SVGElement interface: attribute onsubmit
 PASS SVGElement interface: attribute onsuspend

blink/web_tests/external/wpt/html/dom/idlharness.https_include=(Document_Window)-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 984 tests; 960 PASS, 24 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 984 tests; 966 PASS, 18 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS idl_test setup
 PASS idl_test validation
 PASS Partial interface Document: original interface defined
@@ -273,7 +273,7 @@ FAIL Window interface: attribute onsecuritypolicyviolation assert_own_property:
 PASS Window interface: attribute onseeked
 PASS Window interface: attribute onseeking
 PASS Window interface: attribute onselect
-FAIL Window interface: attribute onslotchange assert_own_property: The global object must have a property "onslotchange" expected property "onslotchange" missing
+PASS Window interface: attribute onslotchange
 PASS Window interface: attribute onstalled
 PASS Window interface: attribute onsubmit
 PASS Window interface: attribute onsuspend
@@ -428,7 +428,7 @@ FAIL Window interface: window must inherit property "onsecuritypolicyviolation"
 PASS Window interface: window must inherit property "onseeked" with the proper type
 PASS Window interface: window must inherit property "onseeking" with the proper type
 PASS Window interface: window must inherit property "onselect" with the proper type
-FAIL Window interface: window must inherit property "onslotchange" with the proper type assert_own_property: expected property "onslotchange" missing
+PASS Window interface: window must inherit property "onslotchange" with the proper type
 PASS Window interface: window must inherit property "onstalled" with the proper type
 PASS Window interface: window must inherit property "onsubmit" with the proper type
 PASS Window interface: window must inherit property "onsuspend" with the proper type
@@ -586,7 +586,7 @@ PASS Document interface: attribute onsecuritypolicyviolation
 PASS Document interface: attribute onseeked
 PASS Document interface: attribute onseeking
 PASS Document interface: attribute onselect
-FAIL Document interface: attribute onslotchange assert_true: The prototype object must have a property "onslotchange" expected true got false
+PASS Document interface: attribute onslotchange
 PASS Document interface: attribute onstalled
 PASS Document interface: attribute onsubmit
 PASS Document interface: attribute onsuspend
@@ -713,7 +713,7 @@ PASS Document interface: iframe.contentDocument must inherit property "onsecurit
 PASS Document interface: iframe.contentDocument must inherit property "onseeked" with the proper type
 PASS Document interface: iframe.contentDocument must inherit property "onseeking" with the proper type
 PASS Document interface: iframe.contentDocument must inherit property "onselect" with the proper type
-FAIL Document interface: iframe.contentDocument must inherit property "onslotchange" with the proper type assert_inherits: property "onslotchange" not found in prototype chain
+PASS Document interface: iframe.contentDocument must inherit property "onslotchange" with the proper type
 PASS Document interface: iframe.contentDocument must inherit property "onstalled" with the proper type
 PASS Document interface: iframe.contentDocument must inherit property "onsubmit" with the proper type
 PASS Document interface: iframe.contentDocument must inherit property "onsuspend" with the proper type
@@ -840,7 +840,7 @@ PASS Document interface: new Document() must inherit property "onsecuritypolicyv
 PASS Document interface: new Document() must inherit property "onseeked" with the proper type
 PASS Document interface: new Document() must inherit property "onseeking" with the proper type
 PASS Document interface: new Document() must inherit property "onselect" with the proper type
-FAIL Document interface: new Document() must inherit property "onslotchange" with the proper type assert_inherits: property "onslotchange" not found in prototype chain
+PASS Document interface: new Document() must inherit property "onslotchange" with the proper type
 PASS Document interface: new Document() must inherit property "onstalled" with the proper type
 PASS Document interface: new Document() must inherit property "onsubmit" with the proper type
 PASS Document interface: new Document() must inherit property "onsuspend" with the proper type
@@ -967,7 +967,7 @@ PASS Document interface: documentWithHandlers must inherit property "onsecurityp
 PASS Document interface: documentWithHandlers must inherit property "onseeked" with the proper type
 PASS Document interface: documentWithHandlers must inherit property "onseeking" with the proper type
 PASS Document interface: documentWithHandlers must inherit property "onselect" with the proper type
-FAIL Document interface: documentWithHandlers must inherit property "onslotchange" with the proper type assert_inherits: property "onslotchange" found on object expected in prototype chain
+PASS Document interface: documentWithHandlers must inherit property "onslotchange" with the proper type
 PASS Document interface: documentWithHandlers must inherit property "onstalled" with the proper type
 PASS Document interface: documentWithHandlers must inherit property "onsubmit" with the proper type
 PASS Document interface: documentWithHandlers must inherit property "onsuspend" with the proper type

blink/web_tests/external/wpt/html/dom/idlharness.https_include=HTML._-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 3772 tests; 3746 PASS, 26 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 3772 tests; 3748 PASS, 24 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS idl_test setup
 PASS idl_test validation
 PASS Partial interface Document: original interface defined
@@ -291,7 +291,7 @@ FAIL HTMLElement interface: attribute onsecuritypolicyviolation assert_true: The
 PASS HTMLElement interface: attribute onseeked
 PASS HTMLElement interface: attribute onseeking
 PASS HTMLElement interface: attribute onselect
-FAIL HTMLElement interface: attribute onslotchange assert_true: The prototype object must have a property "onslotchange" expected true got false
+PASS HTMLElement interface: attribute onslotchange
 PASS HTMLElement interface: attribute onstalled
 PASS HTMLElement interface: attribute onsubmit
 PASS HTMLElement interface: attribute onsuspend
@@ -388,7 +388,7 @@ FAIL HTMLElement interface: document.createElement("noscript") must inherit prop
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onseeked" with the proper type
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onseeking" with the proper type
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onselect" with the proper type
-FAIL HTMLElement interface: document.createElement("noscript") must inherit property "onslotchange" with the proper type assert_inherits: property "onslotchange" not found in prototype chain
+PASS HTMLElement interface: document.createElement("noscript") must inherit property "onslotchange" with the proper type
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onstalled" with the proper type
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onsubmit" with the proper type
 PASS HTMLElement interface: document.createElement("noscript") must inherit property "onsuspend" with the proper type

blink/web_tests/external/wpt/html/webappapis/scripting/events/event-handler-all-global-events-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 335 tests; 319 PASS, 16 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 335 tests; 323 PASS, 12 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS onabort: must be on the appropriate locations for GlobalEventHandlers
 PASS onabort: the default value must be null
 PASS onabort: the content attribute must be compiled into a function as the corresponding property
@@ -270,10 +270,10 @@ PASS onselect: the default value must be null
 PASS onselect: the content attribute must be compiled into a function as the corresponding property
 PASS onselect: the content attribute must execute when an event is dispatched
 PASS onselect: dispatching an Event at a <meta> element must trigger element.onselect
-FAIL onslotchange: must be on the appropriate locations for GlobalEventHandlers assert_true: Window has an own property named "onslotchange" expected true got false
-FAIL onslotchange: the default value must be null assert_equals: The default value of the property is null for a Window instance expected (object) null but got (undefined) undefined
-FAIL onslotchange: the content attribute must be compiled into a function as the corresponding property assert_equals: The onslotchange property must be a function expected "function" but got "undefined"
-FAIL onslotchange: the content attribute must execute when an event is dispatched assert_true: Dispatching an event must run the code expected true got undefined
+PASS onslotchange: must be on the appropriate locations for GlobalEventHandlers
+PASS onslotchange: the default value must be null
+PASS onslotchange: the content attribute must be compiled into a function as the corresponding property
+PASS onslotchange: the content attribute must execute when an event is dispatched
 PASS onslotchange: dispatching an Event at a <meta> element must trigger element.onslotchange
 PASS onstalled: must be on the appropriate locations for GlobalEventHandlers
 PASS onstalled: the default value must be null

blink/web_tests/external/wpt/html/webappapis/scripting/events/event-handler-attributes-body-window-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 327 tests; 309 PASS, 18 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 327 tests; 312 PASS, 15 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS shadowed blur (document.body)
 PASS shadowed error (document.body)
 PASS shadowed focus (document.body)
@@ -71,7 +71,7 @@ FAIL not shadowed securitypolicyviolation (document.body) assert_equals: alterna
 PASS not shadowed seeked (document.body)
 PASS not shadowed seeking (document.body)
 PASS not shadowed select (document.body)
-FAIL not shadowed slotchange (document.body) assert_equals: alternative body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (document.body)
 PASS not shadowed stalled (document.body)
 PASS not shadowed submit (document.body)
 PASS not shadowed suspend (document.body)
@@ -180,7 +180,7 @@ FAIL not shadowed securitypolicyviolation (document.createElement("body")) asser
 PASS not shadowed seeked (document.createElement("body"))
 PASS not shadowed seeking (document.createElement("body"))
 PASS not shadowed select (document.createElement("body"))
-FAIL not shadowed slotchange (document.createElement("body")) assert_equals: body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (document.createElement("body"))
 PASS not shadowed stalled (document.createElement("body"))
 PASS not shadowed submit (document.createElement("body"))
 PASS not shadowed suspend (document.createElement("body"))
@@ -289,7 +289,7 @@ FAIL not shadowed securitypolicyviolation (window) assert_equals: body should re
 PASS not shadowed seeked (window)
 PASS not shadowed seeking (window)
 PASS not shadowed select (window)
-FAIL not shadowed slotchange (window) assert_equals: body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (window)
 PASS not shadowed stalled (window)
 PASS not shadowed submit (window)
 PASS not shadowed suspend (window)

blink/web_tests/external/wpt/html/webappapis/scripting/events/event-handler-attributes-frameset-window-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 327 tests; 309 PASS, 18 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 327 tests; 312 PASS, 15 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS shadowed blur (document.body)
 PASS shadowed error (document.body)
 PASS shadowed focus (document.body)
@@ -71,7 +71,7 @@ FAIL not shadowed securitypolicyviolation (document.body) assert_equals: alterna
 PASS not shadowed seeked (document.body)
 PASS not shadowed seeking (document.body)
 PASS not shadowed select (document.body)
-FAIL not shadowed slotchange (document.body) assert_equals: alternative body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (document.body)
 PASS not shadowed stalled (document.body)
 PASS not shadowed submit (document.body)
 PASS not shadowed suspend (document.body)
@@ -180,7 +180,7 @@ FAIL not shadowed securitypolicyviolation (document.createElement("frameset")) a
 PASS not shadowed seeked (document.createElement("frameset"))
 PASS not shadowed seeking (document.createElement("frameset"))
 PASS not shadowed select (document.createElement("frameset"))
-FAIL not shadowed slotchange (document.createElement("frameset")) assert_equals: body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (document.createElement("frameset"))
 PASS not shadowed stalled (document.createElement("frameset"))
 PASS not shadowed submit (document.createElement("frameset"))
 PASS not shadowed suspend (document.createElement("frameset"))
@@ -289,7 +289,7 @@ FAIL not shadowed securitypolicyviolation (window) assert_equals: body should re
 PASS not shadowed seeked (window)
 PASS not shadowed seeking (window)
 PASS not shadowed select (window)
-FAIL not shadowed slotchange (window) assert_equals: body should reflect expected (object) null but got (undefined) undefined
+PASS not shadowed slotchange (window)
 PASS not shadowed stalled (window)
 PASS not shadowed submit (window)
 PASS not shadowed suspend (window)

blink/web_tests/external/wpt/html/webappapis/scripting/events/event-handler-attributes-windowless-body-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 218 tests; 210 PASS, 8 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 218 tests; 212 PASS, 6 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS Return null when getting the blur event handler of a windowless body
 PASS Ignore setting of blur window event handlers on windowless body
 PASS Return null when getting the error event handler of a windowless body
@@ -93,7 +93,7 @@ FAIL securitypolicyviolation is unaffected on a windowless body assert_equals: e
 PASS seeked is unaffected on a windowless body
 PASS seeking is unaffected on a windowless body
 PASS select is unaffected on a windowless body
-FAIL slotchange is unaffected on a windowless body assert_equals: expected (object) null but got (undefined) undefined
+PASS slotchange is unaffected on a windowless body
 PASS stalled is unaffected on a windowless body
 PASS submit is unaffected on a windowless body
 PASS suspend is unaffected on a windowless body
@@ -202,7 +202,7 @@ FAIL securitypolicyviolation is unaffected on a windowless frameset assert_equal
 PASS seeked is unaffected on a windowless frameset
 PASS seeking is unaffected on a windowless frameset
 PASS select is unaffected on a windowless frameset
-FAIL slotchange is unaffected on a windowless frameset assert_equals: expected (object) null but got (undefined) undefined
+PASS slotchange is unaffected on a windowless frameset
 PASS stalled is unaffected on a windowless frameset
 PASS submit is unaffected on a windowless frameset
 PASS suspend is unaffected on a windowless frameset