The bindings generator has an adhoc method for controlling the generation of the associated C++ enumeration value name from a string value. Sometimes, it would better to have local control over the naming. Implementing `[ImplementedAs]` for enumeration values, whose presence would over rule the adhoc method, would be better.
<rdar://problem/118909721>
Pull request: https://github.com/WebKit/WebKit/pull/21038