reservedSchemes constant
The schemes the platform and the engine read themselves, which a
plugin from outside may not take: a source registered for one is asked
before the fallback, so it would take every such load away from the
engine, and a scheme the engine adds in a minor (hub) would stop an
application at start with "already has a source".
Frozen at 1.0.0, as PluginManifest.reservedAreas is: a scheme
the engine brings later goes under f3d-.
Implementation
static const Set<String> reservedSchemes = <String>{
'asset',
'blob',
'data',
'f3d',
'file',
'http',
'https',
'hub',
'package',
};