A JSON BasicMessageChannel for system events.
Events are exposed as Maps with string keys. The
type key specifies
the type of the event; the currently supported system event types are
those listed below. A handler can be registered using
memoryPressure: Indicates that the operating system would like applications to release caches to free up more memory. See WidgetsBindingObserver.didHaveMemoryPressure, which triggers whenever a message is received on this channel.
static const BasicMessageChannel<Object?> system = BasicMessageChannel<Object?>( 'flutter/system', JSONMessageCodec(), );