Adding the step to handle user prompts for screenshots

index.html

@@ -8936,6 +8936,8 @@ <h3><dfn>Take Screenshot</dfn></h3>
  <li><p>If the <a>current top-level browsing context</a> is <a>no longer open</a>,
   return <a>error</a> with <a>error code</a> <a>no such window</a>.
 
+ <li><p><a>Handle any user prompts</a> and return its value if it is an <a>error</a>.
+
  <li><p>When the user agent is next to <a>run the animation frame callbacks</a>:
   <ol>
    <li><p>Let <var>root rect</var> be the <a>current top-level browsing context</a>’s
@@ -8989,7 +8991,9 @@ <h3><dfn>Take Element Screenshot</dfn></h3>
 
  <li><p>If the <a>current browsing context</a> is <a>no longer open</a>,
   return <a>error</a> with <a>error code</a> <a>no such window</a>.
-
+
+ <li><p><a>Handle any user prompts</a> and return its value if it is an <a>error</a>.
+
  <li><p>Let <var>element</var> be the result of
   <a>trying</a> to <a>get a known connected element</a>
   with <a>url variable</a> <var>element id</var>.