Fix #19137: handle when regexp doesn't match in constructorNameFallback

tests/html/websocket_test.dart

 library WebSocketTest;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 
 main() {
 
   useHtmlIndividualConfiguration();
 
   group('supported', () {
@@ skipping 17 matching lines @@
     if (WebSocket.supported) {
       test('echo', () {
         var socket = new WebSocket('ws://${window.location.host}/ws');
 
         socket.onOpen.first.then((_) {
           socket.send('hello!');
         });
 
         return socket.onMessage.first.then((MessageEvent e) {
           expect(e.data, 'hello!');
+          socket.close();
+        });
+      });
+
+      test('error', () {
+        // The server supports ws, but not wss, this will yeild an error that we

[sra1, 2015/12/10 05:30:38]

yield

[Siggi Cherem (dart-lang), 2015/12/10 20:27:39]

Done.

+        // expect to catch below.
+        var socket = new WebSocket('wss://${window.location.host}/ws');
+        socket.onOpen.first.then((_) => socket.send('hello!'));
+        return socket.onError.first.then((e) {
+          // This test checks fo regressions of issue #19137: on Safari 7 an
+          // error like this one would be seen, but dart2js's logic to provide
+          // an interceptor failed while trying to compute the name of the
+          // constructor.

[sra1, 2015/12/10 05:30:38]

I'm not clear how this fails / passes. Can you explain?

[Siggi Cherem (dart-lang), 2015/12/10 20:27:39]

Done - added more details.

I was not able to verify that this problem occurs, but I was able to reach the
enclosing function in FF, and by stepping through it and changing the result of
some conditions, I was able to validate that the erroneous code path could be
exercised.

+          print('$e was caught');
+          socket.close();
         });
       });
     }
   });
 }