Fix for listening to custom streams in DWDS.

[CoderDake]

Fixes Dart-Code/Dart-Code#4414 (comment)

When listening to a stream, DDS does a streamListen on the VMService. If the VMService, doesn't recognize the stream it will respond with kInvalidParams. This lets DDS know that the stream is nonstandard, so it can handle the events for that stream on it's own.

This PR changes DWDS to behave like the VMService in this regard. Fixing this will allow us to streamListen on custom streams using DWDS.

[CoderDake]

CC: @DanTup @bkonyi @elliette

[DanTup]

Thanks! This change LGTM (it's what I tested locally and definitely worked), but you may want the opinion of someone more familiar with DWDS than I 🙂

[elliette]

Thanks! Could you add a test case? Here are where we have test cases for the other stream event types:

webdev/dwds/test/chrome_proxy_service_test.dart

Lines 1973 to 1998 in 85f35d4

	test('Timeline', () async {
	expect(service.streamListen('Timeline'), completion(_isSuccess));
	});
	test('Stdout', () async {
	expect(service.streamListen('Stdout'), completion(_isSuccess));
	expect(
	service.onEvent('Stdout'),
	emitsThrough(predicate((Event event) =>
	event.kind == EventKind.kWriteEvent &&
	String.fromCharCodes(base64.decode(event.bytes!))
	.contains('hello'))));
	await context.tabConnection.runtime.evaluate('console.log("hello");');
	});
	test('Stderr', () async {
	expect(service.streamListen('Stderr'), completion(_isSuccess));
	final stderrStream = service.onEvent('Stderr');
	expect(
	stderrStream,
	emitsThrough(predicate((Event event) =>
	event.kind == EventKind.kWriteEvent &&
	String.fromCharCodes(base64.decode(event.bytes!))
	.contains('Error'))));
	await context.tabConnection.runtime.evaluate('console.error("Error");');
	});

[bkonyi]

LGTM pending Elliott's approval

[elliette]

We handle the VM stream (which is why the test is failing)