Function updateDocumentVisibility

test/unit/test-ampdoc.js:470–475

(doc, visibilityState)

  });

  function updateDocumentVisibility(doc, visibilityState) {
    doc.visibilityState = visibilityState;
    if (doc.addEventListener.args.length > 0) {
      doc.addEventListener.args[0][1]();
    }
  }

  it('should set up and destroy listeners', () => {
    // 1 for top, 1 for embedSameWindow.