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chromium/third_party/blink/renderer/core/testing/data/wide_document_width_viewport.html 

<html>
  <head>
    <meta name='viewport' content='width=device-width,initial-scale=0.25' />
  </head>
  <body style="margin:0px;">
    <img width="800px" height="800px" src="white-1x1.png">Wide img forcing page to widen</img>
  </body>
</html>