Tests that DOM.setInspectedNode works for before, after, and marker pseudo elements.
Inspected ::after: {"isCSSPseudoElement":true,"type":"::after","originatingTagName":"DIV"}
Inspected ::before: {"isCSSPseudoElement":true,"type":"::before","originatingTagName":"DIV"}
Inspected ::marker: {"isCSSPseudoElement":true,"type":"::marker","originatingTagName":"DIV"}