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 <title>Custom Elements: create an element for a token must increment and decrement document's throw-on-dynamic-markup-insertion counter</title>
 <meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
 <meta name="assert" content="Invoking document.open, document.write, document.writeln, and document.write must throw an exception when the HTML parser is creating a custom element for a token">
 <meta name="help" content="https://html.spec.whatwg.org/multipage