Remove deprecated string features.

tests/standalone/io/socket_stream_close_test.dart

Index: tests/standalone/io/socket_stream_close_test.dart
diff --git a/tests/standalone/io/socket_stream_close_test.dart b/tests/standalone/io/socket_stream_close_test.dart
index 4082c81ac8427e98f16a1bf09b93dd3ad46d2c0e..b52e54a50706b699bb23db0598fd456f68281856 100644
--- a/tests/standalone/io/socket_stream_close_test.dart
+++ b/tests/standalone/io/socket_stream_close_test.dart
@@ -110,7 +110,7 @@ class SocketClose {
           proceed();
           break;
         case 1:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.inputStream.close();
             proceed();
@@ -119,20 +119,20 @@ class SocketClose {
         case 2:
         case 3:
         case 4:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           break;
         case 5:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.outputStream.close();
           };
           break;
         case 6:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           break;
         case 7:
         case 8:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.outputStream.close();
           };
@@ -256,7 +256,7 @@ class SocketCloseServer {
         case 3:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.onNoPendingWrites = () {
               connection.inputStream.close();
             };
@@ -265,21 +265,21 @@ class SocketCloseServer {
         case 4:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.inputStream.close();
           });
           break;
         case 5:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
           });
           break;
         case 6:
         case 7:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.onNoPendingWrites = () {
               connection.outputStream.close();
             };
@@ -288,7 +288,7 @@ class SocketCloseServer {
         case 8:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.close();
           });
           break;