Use onClosed instead of onError in the WebSocket classes.

tests/standalone/io/web_socket_test.dart

Index: tests/standalone/io/web_socket_test.dart
diff --git a/tests/standalone/io/web_socket_test.dart b/tests/standalone/io/web_socket_test.dart
index 6406dfb646d9b04e5bde0f8ae22118bf22181681..efff5f2006b126e39e3a2bc67be07ebe3bd8eb40 100644
--- a/tests/standalone/io/web_socket_test.dart
+++ b/tests/standalone/io/web_socket_test.dart
@@ -19,8 +19,8 @@ void testRequestResponseClientCloses(
     var count = 0;
     conn.onMessage = (Object message) => conn.send(message);
     conn.onClosed = (status, reason) {
-      Expect.equals(closeStatus, status);
-      Expect.equals(closeReason, reason);
+      Expect.equals(closeStatus === null ? 1005 : closeStatus, status);
+      Expect.equals(closeReason === null ? "" : closeReason, reason);
     };
   };
   server.defaultRequestHandler = wsHandler.onRequest;
@@ -42,8 +42,8 @@ void testRequestResponseClientCloses(
       }
     };
     wsconn.onClosed = (status, reason) {
-      Expect.equals(closeStatus, status);
-      Expect.isNull(reason);
+      Expect.equals(closeStatus === null ? 1005 : closeStatus, status);
+      Expect.equals("", reason);
       closeCount++;
       if (closeCount == totalConnections) {
         client.shutdown();
@@ -78,8 +78,8 @@ void testRequestResponseServerCloses(
       }
     };
     conn.onClosed = (status, reason) {
-      Expect.equals(closeStatus, status);
-      Expect.isNull(reason);
+      Expect.equals(closeStatus === null ? 1005 : closeStatus, status);
+      Expect.equals("", reason);
       closeCount++;
       if (closeCount == totalConnections) {
         client.shutdown();
@@ -95,8 +95,8 @@ void testRequestResponseServerCloses(
     WebSocketClientConnection wsconn = new WebSocketClientConnection(conn);
     wsconn.onMessage = (message) => wsconn.send(message);
     wsconn.onClosed = (status, reason) {
-      Expect.equals(closeStatus, status);
-      Expect.equals(closeReason, reason);
+      Expect.equals(closeStatus === null ? 1005 : closeStatus, status);
+      Expect.equals(closeReason === null ? "" : closeReason, reason);
     };
   }
 }
@@ -263,7 +263,7 @@ void testW3CInterface(
     };
     conn.onClosed = (status, reason) {
       Expect.equals(closeStatus, status);
-      Expect.isNull(reason);
+      Expect.equals("", reason);
       closeCount++;
       if (closeCount == totalConnections) {
         server.close();