Fix perform and release actions for valid browsing context check and …

…handle alert step (w3c#1877)

index.html

@@ -10270,6 +10270,12 @@ <h3><dfn>Perform Actions</dfn></h3>
 variables</var> and <var>parameters</var> are:
 
 <ol class="algorithm">
+  <li><p>If <var>session</var>&apos;s <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>Try</a> to <a>handle any user prompts</a> with <var>session</var>.
+
   <li><p>Let <var>input state</var> be the result of <a>get the input
   state</a> with <var>session</var>
   and <var>session</var>&apos;s <a>current top-level browsing
@@ -10284,13 +10290,6 @@ <h3><dfn>Perform Actions</dfn></h3>
   to <a>extract an action sequence</a> with <var>input state</var>,
   <var>parameters</var>, and <var>actions options</var>.
 
- <li><p>If <var>session</var>&apos;s <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>Try</a> to <a>handle any user prompts</a>
-  with <var>session</var>.
-
  <li><p><a>Dispatch actions</a> with <var>input state</var>,
   <var>actions by tick</var>, <a>current browsing context</a>,
   and <var>actions options</var>. If this results in an <a>error</a>
@@ -10331,6 +10330,8 @@ <h3><dfn>Release Actions</dfn></h3>
   is <a>no longer open</a>, return <a>error</a> with <a>error
   code</a> <a>no such window</a>.
 
+  <li><p><a>Try</a> to <a>handle any user prompts</a> with <var>session</var>.
+
  <li><p>Let <var>input state</var> be the result of <a>get the input state</a>
   with <a>session</a> and <a>current top-level browsing context</a>.