Fix typo that has crept into string input stream.

tests/standalone/src/io/StringStreamTest.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #import("dart:io");
 
 void testUtf8() {
   List<int> data = [0x01,
                     0x7f,
                     0xc2, 0x80,
@@ skipping 147 matching lines @@
   void streamClosed() {
     Expect.equals(4, stage);
     Expect.equals(true, stream.closed);
   }
 
   stream.onLine = stringData;
   stream.onClosed = streamClosed;
   s.write("Line1\nLine2\r\nLine3\rLi".charCodes());
 }
 
+class TestException {
+  TestException();
+}
+
+class ErrorInputStream implements InputStream {
+  ErrorInputStream();
+  List<int> read([int len]) => null;
+  int readInto(List<int> buffer, [int offset, int len]) => 0;
+  int available() => 0;
+  void pipe(OutputStream output, [bool close]){ }
+  void close() { }
+  bool get closed() => true;
+  void set onData(void callback()) { }
+  void set onClosed(void callback()) { }
+  void set onError(void callback(Exception e)) {
+    callback(new TestException());
+  }
+}
+
+testErrorHandler() {
+  var errors = 0;
+  var stream = new StringInputStream(new ErrorInputStream());
+  stream.onError = (e) {
+    errors++;
+    Expect.isTrue(e is TestException);
+  };
+  Expect.equals(1, errors);
+}
+
 main() {
   testUtf8();
   testLatin1();
   testAscii();
   testReadLine1();
   testReadLine2();
+  testErrorHandler();
 }