chromium/third_party/blink/web_tests/fast/forms/mailto/get-overwrite-query.html

<body onload="test()">
<form method="get" action="mailto:[email protected][email protected]&amp;body=Body">
<input type="text" size="10" maxlength="40" name="to" value="[email protected]">
<input type="submit" value="Send"> 
</form>
<div>Expected results when clicking "Send" button:  A new mail message is created with an empty body, and two addressees.</div>
<script>
function test() {
  if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitForPolicyDelegate();
    document.getElementsByTagName("form")[0].submit();
  }
}
</script>