chromium/third_party/blink/web_tests/http/tests/security/cross-frame-mouse-source-capabilities.html

<!doctype html>
<html>
<head>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
var button = null;

function clickButton() {
    if (!button)
        button = document.querySelector("button");
    button.click();
}

function handler(event) {
    assert_not_equals(event.sourceCapabilities, null);
    event.sourceCapabilities.customProperty = 42;
}

async_test(function(t) {
    window.addEventListener('message', function(evt) {
        if (evt.data === "start") {
            setTimeout(clickButton);
            return;
        }

        assert_equals(evt.data, undefined);
        // Check that |sourceCapabilities| is same within the context
        // of the same window. We may want to weaken this further and
        // not insist on sameness across dispatched events.
        button.onclick = function (event) {
            assert_not_equals(event.sourceCapabilities, null);
            assert_equals(event.sourceCapabilities.customProperty, 42);
            t.done();
        };
        button.click();
    });

}, 'Test that event sourceCapabilities object is not shared cross-origin');
</script>
</head>
<body>
<button onclick="handler(event)"></button>
<iframe src="http://localhost:8000/security/resources/cross-frame-mouse-source-capabilities.html"></iframe>
</body>
</html>