Make IOSink implement StringSink

tests/standalone/io/http_client_request_test.dart

Index: tests/standalone/io/http_client_request_test.dart
diff --git a/tests/standalone/io/http_client_request_test.dart b/tests/standalone/io/http_client_request_test.dart
index 02d0a86ce4a65618f1d5259afe872425a55aecdf..d2c9236c446109448b1e291e164cbac07759cd6d 100644
--- a/tests/standalone/io/http_client_request_test.dart
+++ b/tests/standalone/io/http_client_request_test.dart
@@ -46,7 +46,7 @@ void testBadResponseAdd() {
   testClientRequest((request) {
     var port = new ReceivePort();
     request.contentLength = 0;
-    request.add([0]);
+    request.writeBytes([0]);
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);
@@ -56,8 +56,8 @@ void testBadResponseAdd() {
   testClientRequest((request) {
     var port = new ReceivePort();
     request.contentLength = 5;
-    request.add([0, 0, 0]);
-    request.add([0, 0, 0]);
+    request.writeBytes([0, 0, 0]);
+    request.writeBytes([0, 0, 0]);
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);
@@ -67,9 +67,9 @@ void testBadResponseAdd() {
   testClientRequest((request) {
     var port = new ReceivePort();
     request.contentLength = 0;
-    request.add(new Uint8List(64 * 1024));
-    request.add(new Uint8List(64 * 1024));
-    request.add(new Uint8List(64 * 1024));
+    request.writeBytes(new Uint8List(64 * 1024));
+    request.writeBytes(new Uint8List(64 * 1024));
+    request.writeBytes(new Uint8List(64 * 1024));
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);
@@ -91,7 +91,7 @@ void testBadResponseClose() {
   testClientRequest((request) {
     var port = new ReceivePort();
     request.contentLength = 5;
-    request.add([0]);
+    request.writeBytes([0]);
     request.close();
     request.done.catchError((error) {
       port.close();