Initializes the core default styles for the charts classes. Each chart and element is responsible for initializing their own
style values, but they rely on the common values computed by the HaloDefaults class.
Creates a CSSStyleDeclaration object or returns an existing one.
Parameters
selectorName:String — The name of the selector to return. If no existing CSSStyleDeclaration object matches
this name, this method creates a new one and returns it.
styleManager:IStyleManager2 — The styleManager instance to be used for getting and setting style declarations.
Returns
CSSStyleDeclaration — The CSSStyleDeclaration object that matches the provided selector name. If no CSSStyleDeclaration object matches
that name, this method creates a new one and returns it.