Use event handler content attribute concept

spec/index.bs

@@ -682,8 +682,6 @@ Its value is initially « ».
         </table>
     1. Return |expectedType|.
 
-    Note: Step 3 is a special case for <a href=https://html.spec.whatwg.org/#event-handler-name>event handler names</a>, as they always start with "on".
-
     <div class="example" id="get-property-type-example">
     <xmp highlight="js">
     trustedTypes.getPropertyType('div', 'innerHTML'); // "TrustedHTML"
@@ -701,7 +699,6 @@ Its value is initially « ».
 
     1. Set |localName| to |tagName| in [=ASCII lowercase=].
     1. Set |attribute| to |attribute| in [=ASCII lowercase=].
-    1. If |attribute| starts with "on", then return {{TrustedScript}}.
     1. If |elementNs| is an empty string, set |elementNs| to [=HTML namespace=].
     1. If |attrNs| is an empty string, set |attrNs| to null.
     1. Let |interface| be the [=element interface=] for |localName| and |elementNs|.
@@ -713,8 +710,6 @@ Its value is initially « ».
     1. If |attributeData| is not null, then set |expectedType| to the value of the third member of |attributeData|.
     1. Return |expectedType|.
 
-    Note: Step 3 is a special case for <a href=https://html.spec.whatwg.org/#event-handler-name>event handler names</a>, as they always start with "on".
-
     <div class="example" id="get-attribute-type-example">
     <xmp highlight="js">
     trustedTypes.getAttributeType('script', 'src'); // "TrustedScriptURL"
@@ -1110,6 +1105,8 @@ To <dfn abstract-op export>get Trusted Types-compliant attribute value</dfn> on
 To <dfn abstract-op>Get Trusted Type data for attribute</dfn> given |element|, |attribute|, |attributeNs|, perform the following steps:
 
 1. Let |data| be null.
+1. If |attributeNs| is null, and |attribute| is the name of an [=event handler content attribute=], then:
+    1. Return ({{Element}}, null, {{TrustedScript}}, "Element " + |attribute|).
 1. Find the row in the following table, where |element| is in the first column, |attributeNs| is in the second column,
     and |attribute| is in the third column.
     If a matching row is found, set |data| to that row.
@@ -1127,8 +1124,6 @@ To <dfn abstract-op>Get Trusted Type data for attribute</dfn> given |element|, |
 
 1. Return |data|.
 
-Issue: This algorithm should account for event handler attributes. See https://github.com/w3c/trusted-types/issues/474
-
 # Integrations # {#integrations}
 
 <pre class="idl">