Hammerhead is missed after 'document.close' in Firefox

[miherlosev]

Test for reproduce

test('test', function () {
    return createTestIframe()
        .then(function (iframe) {
            iframe.contentDocument.open();
            iframe.contentDocument.write('Hello!');
            iframe.contentDocument.close();

            var iframeHammerhead = iframe.contentWindow['%hammerhead%'];
            ok(iframeHammerhead);
        });
});

[lock]

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