isIgnoredBackend static method
True when requested asks for something other than what an embedder
actually uses, so a caller can be told once that it changed nothing.
Derived from _resolvedBackend rather than repeating the CPU constant, so
the fact still has exactly one site: the day that method returns the
request, this stops speaking on its own.
Implementation
static bool isIgnoredBackend(PreferredBackend? requested) =>
requested != null && _resolvedBackend(requested) != requested;