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

<body>
  <object data='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==' width="500" height="500" id="obj">Fallback content</object>
</body>