Fix return value checking for unload cancelation

Closes #11357.

Author: domenic

source

@@ -99109,7 +99109,7 @@ interface <dfn interface>NotRestoredReasons</dfn> {
    document</span>'s <span>inclusive descendant navigables</span>.</p></li>
 
    <li><p>If the result of <span>checking if unloading is canceled</span> for <var>toUnload</var> is
-   true, then return.</p></li>
+   not "<code data-x="">continue</code>", then return.</p></li>
 
    <li>
     <p><span data-x="tn-append-session-history-traversal-steps">Append the following session history
@@ -101592,8 +101592,9 @@ location.href = '#foo';</code></pre>
      document</span>'s <span>inclusive descendant navigables</span>.</p>
 
      <li>
-      <p>If <var>unloadPromptCanceled</var> is true, or <var>navigable</var>'s <span>ongoing
-      navigation</span> is no longer <var>navigationId</var>, then:</p>
+      <p>If <var>unloadPromptCanceled</var> is not "<code data-x="">continue</code>", or
+      <var>navigable</var>'s <span>ongoing navigation</span> is no longer
+      <var>navigationId</var>:</p>
 
       <ol>
        <li><p>Invoke <span>WebDriver BiDi navigation failed</span> with <var>navigable</var> and a