
slotToContent is code that should only be executed in Polymer 1. It is weird that splitting up a CSS rule into two would help, but maybe that has to do with ::slotted() descendants not being supported at all: https://polymer-library.polymer-project.org/2.0/docs/upgrade#replace-content-selectors "In shadow DOM v1, you cannot select a descendant of a top-level distributed child. No selectors can follow the ::slotted() selector." Bug: Issue 11067 Bug: Issue 11068 Change-Id: Ibb9ed9a5749a3bb94eff7736c3a9f746c83f37f9