It's invalid to use 2 pseudoelements in a selector but if somehow it becomes valid, it should not expose the internal structure of the shadow tree.

Summary

Harness status: OK

Found 2 tests

Details

ResultTest NameMessage
Pass::part cannot be chained to reach elements in the inner host
Asserts run
Pass
assert_equals("rgb(0, 128, 0)", "rgb(0, 128, 0)")
    at Test.<anonymous> ( /css/css-shadow-parts/chaining-invalid-selector.html:34:9)
PassChained ::part selectors are dropped
Asserts run
Pass
assert_equals(0, 0)
    at Test.<anonymous> ( /css/css-shadow-parts/chaining-invalid-selector.html:37:9)