Remove deprecated string features.

tests/standalone/io/secure_server_stream_test.dart

Index: tests/standalone/io/secure_server_stream_test.dart
diff --git a/tests/standalone/io/secure_server_stream_test.dart b/tests/standalone/io/secure_server_stream_test.dart
index d99e93e1d22d519dc22a56f7c5ddac0cadbafaa7..170c5967e808301189ea5af80b2213c6f5678ab3 100644
--- a/tests/standalone/io/secure_server_stream_test.dart
+++ b/tests/standalone/io/secure_server_stream_test.dart
@@ -19,7 +19,7 @@ class SecureTestServer {
     input.onClosed = () {
       Expect.isTrue(received.contains("Hello from client "));
       String name = received.substring(received.indexOf("client ") + 7);
-      connection.outputStream.write("Welcome, client $name".charCodes);
+      connection.outputStream.write("Welcome, client $name".codeUnits);
       connection.outputStream.close();
     };
   }
@@ -48,7 +48,7 @@ class SecureTestClient {
   SecureTestClient(int this.port, String this.name) {
     socket = new SecureSocket(HOST_NAME, port);
     numRequests++;
-    socket.outputStream.write("Hello from client $name".charCodes);
+    socket.outputStream.write("Hello from client $name".codeUnits);
     socket.outputStream.close();
     socket.inputStream.onData = () {
       reply = reply.concat(new String.fromCharCodes(socket.inputStream.read()));