Restricted pseudo-elements (like ::placeholder, ::first-letter,
::first-line, and ::selection) use property whitelists. These
whitelists did not include transition or animation properties.
As a result, pseudo_element_supports_property() rejected transition and
animation declarations during cascade filtering. This caused
transition-duration and transition-delay to resolve to their initial
values (0s), which triggered the zero-second optimization in
compute_transitioned_properties() and prevented transition
registration.
This change introduces a fast-path check in the generated function
pseudo_element_supports_property() to automatically accept all CSS
transition and animation properties on any styleable pseudo-element.
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