bufferEarlyErrorForTest function
Test-only seam to push an error into the buffer as the early handlers would,
so the bounded-buffer / flush tests do not need to drive real
FlutterError.onError (Issue 16/82).
Implementation
@visibleForTesting
void bufferEarlyErrorForTest(Object error, [StackTrace? stackTrace]) {
_bufferEarlyError(error, stackTrace);
}