Make some required parameters optional

dwds/lib/dwds.dart

@@ -47,20 +47,23 @@ class Dwds {
   }
 
   static Future<Dwds> start({
-    @required String hostname,
     @required int applicationPort,
     @required int assetServerPort,
     @required String applicationTarget,
-    @required ReloadConfiguration reloadConfiguration,
     @required Stream<BuildResult> buildResults,
     @required ConnectionProvider chromeConnection,
-    @required bool serveDevTools,
-    @required LogWriter logWriter,
-    @required bool verbose,
-    @optional bool enableDebugExtension,
+    String hostname,
+    ReloadConfiguration reloadConfiguration,
+    bool serveDevTools,
+    LogWriter logWriter,
+    bool verbose,
+    bool enableDebugExtension,
   }) async {
-    String extensionHostname;
-    int extensionPort;
+    hostname ??= 'localhost';
+    reloadConfiguration ??= ReloadConfiguration.none;
+    serveDevTools ??= false;
+    logWriter ??= (level, message) => print(message);
+    verbose ??= false;
     enableDebugExtension ??= false;
     var assetHandler = AssetHandler(
       assetServerPort,
@@ -71,6 +74,8 @@ class Dwds {
     var cascade = Cascade();
     var pipeline = const Pipeline();
 
+    String extensionHostname;
+    int extensionPort;
     if (enableDebugExtension) {
       var extensionBackend = await ExtensionBackend.start();
       extensionHostname = extensionBackend.hostname;

dwds/test/fixtures/context.dart

@@ -84,12 +84,9 @@ class TestContext {
     var connection = ChromeConnection('localhost', debugPort);
 
     testServer = await TestServer.start(
-      'localhost',
       port,
       daemonPort(workingDirectory),
       pathToServe,
-      ReloadConfiguration.none,
-      false,
       daemonClient.buildResults,
       () async => connection,
     );

dwds/test/fixtures/server.dart

@@ -41,12 +41,9 @@ class TestServer {
   }
 
   static Future<TestServer> start(
-    String hostname,
     int port,
     int assetServerPort,
     String target,
-    ReloadConfiguration reload,
-    bool startDevTools,
     Stream<BuildResults> buildResults,
     Future<ChromeConnection> Function() chromeConnection,
   ) async {
@@ -56,19 +53,16 @@ class TestServer {
         results.results.firstWhere((result) => result.target == target));
 
     var dwds = await Dwds.start(
-      hostname: hostname,
       applicationPort: port,
       applicationTarget: target,
       assetServerPort: assetServerPort,
       buildResults: filteredBuildResults,
       chromeConnection: chromeConnection,
       logWriter: (level, message) => printOnFailure(message),
-      reloadConfiguration: reload,
-      serveDevTools: startDevTools,
       verbose: true,
     );
 
-    var server = await HttpMultiServer.bind(hostname, port);
+    var server = await HttpMultiServer.bind('localhost', port);
     shelf_io.serveRequests(server, pipeline.addHandler(dwds.handler));
     return TestServer._(
       target,