RTE uses JScodeLibArray to insert CSS
In tx_rtehtmlarea_base, the RTE uses $GLOBALS['SOBE']->doc->JScodeLibArray to insert CSS into the page header. This was added in revision 4298.
I'm attaching a patch that uses $this->TCEform->additionalCode_pre and works correctly in my testing in both the frontend and backend (I am seeing problems with the RTE in IRRE child records but that seems to occur with and without my patch).
(issue imported from #M9613)