Test basic seamless auto-sizing-to-content functionality.
PASS iframe.seamless is true
PASS window.getComputedStyle(iframe).display is "block"
PASS window.getComputedStyle(iframe).width is "200px"
PASS window.getComputedStyle(iframe).height is "100px"
PASS window.getComputedStyle(iframe).height is "200px"
PASS window.getComputedStyle(iframe).width is "100px"