Make document.open() set the document to no-quirks

Per investigation in #3818, this change aligns the behavior of
document.open() with Chrome and Safari.

Tests: web-platform-tests/wpt#10679.

Closes #3831.

source

@@ -90994,6 +90994,8 @@ document.body.appendChild(frame)</code></pre>
    <li><p>If <var>document</var>'s <span>iframe load in progress</span> flag is set, then set
    <var>document</var>'s <span>mute iframe load</span> flag.</p></li>
 
+   <li><p>Set <var>document</var> to <span>no-quirks mode</span>.</p></li>
+
    <li><p>Create a new <span>HTML parser</span> and associate it with <var>document</var>. This is a
    <dfn>script-created parser</dfn> (meaning that it can be closed by the <code
    data-x="dom-document-open">document.open()</code> and <code