Clarify custom element reaction arguments passed

Closes #2299.

source

@@ -66794,23 +66794,26 @@ customElements.define("x-foo", class extends HTMLElement {
 
   <ul>
    <li><p>When <span data-x="custom-element-upgrades">upgraded</span>, its <span data-x="custom
-   element constructor">constructor</span> is run.</p></li>
+   element constructor">constructor</span> is run, with no arguments.</p></li>
 
    <li><p>When it <span>becomes connected</span>, its <code data-x="">connectedCallback</code> is
-   run.</p></li>
+   called, with no arguments.</p></li>
 
    <li><p>When it <span>becomes disconnected</span>, its <code data-x="">disconnectedCallback</code>
-   is run.</p></li>
+   is called, with no arguments.</p></li>
 
    <li><p>When it is <span data-x="concept-node-adopt">adopted</span> into a new document, its <code
-   data-x="">adoptedCallback</code> is run.</p></li>
+   data-x="">adoptedCallback</code> is called, given the old document and new document as
+   arguments.</p></li>
 
    <li><p>When any of its attributes are <span
    data-x="concept-element-attributes-change">changed</span>, <span
    data-x="concept-element-attributes-append">appended</span>, <span
    data-x="concept-element-attributes-remove">removed</span>, or <span
    data-x="concept-element-attributes-replace">replaced</span>, its <code
-   data-x="">attributeChangedCallback</code> is run.</p></li>
+   data-x="">attributeChangedCallback</code> is called, given the attribute's local name, old value,
+   new value, and namespace as arguments. (An attribute's old or new value is considered to be null
+   when the attribute is added or removed, respectively.)</p></li>
   </ul>
 
   <p>We call these reactions collectively <dfn data-x="concept-custom-element-reaction">custom
@@ -120885,6 +120888,7 @@ INSERT INTERFACES HERE
   Stuart Parmenter,
   Subramanian Peruvemba,
   Sudhanshu Jaiswal,
+  sudokus999, <!-- GitHub -->
   Sunava Dutta,
   Susan Borgrink,
   Susan <!--G.--> Lesch,