| This test passes if there is not crash and there is a TypeError exception. This verifies that attributeStyleMap.append throws an exception when appending a CSSVariableReferenceValue property | |
| On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". | |
| PASS p.attributeStyleMap.append('background-size', body.computedStyleMap().get('-webkit-mask-position')) threw exception TypeError: Values cannot contain a CSSVariableReferenceValue. | |
| PASS successfullyParsed is true | |
| TEST COMPLETE | |