We need to provide content assist for the list of property names for a given element in TSS files.
backgroundColor is the token we'd suggest.
We should take the string which is the key of the surrounding object, convert it to a fully qualified type name (see
TISTUD-2783), then query the list of properties for that type.
If the string is not the name of a type, but is a class or id, we need to query the class/id index from the view files to resolve it to the type it is hanging off.