Remove deprecated StringBuffer.add, addAll and addCharCode.

sdk/lib/io/websocket_impl.dart

Index: sdk/lib/io/websocket_impl.dart
diff --git a/sdk/lib/io/websocket_impl.dart b/sdk/lib/io/websocket_impl.dart
index b7ca9a066c4832ad68d853317655f2aa801d3a01..3d14fa3f4ad185e33076de1559856c46aa8355af 100644
--- a/sdk/lib/io/websocket_impl.dart
+++ b/sdk/lib/io/websocket_impl.dart
@@ -186,7 +186,7 @@ class _WebSocketProtocolTransformer extends StreamEventTransformer {
                   throw new WebSocketException("Protocol error");
 
                 case _WebSocketMessageType.TEXT:
-                  _buffer.add(_decodeString(buffer.getRange(index, payload)));
+                  _buffer.write(_decodeString(buffer.getRange(index, payload)));
                   index += payload;
                   if (_remainingPayloadBytes == 0) {
                     _messageFrameEnd(sink);
@@ -194,7 +194,7 @@ class _WebSocketProtocolTransformer extends StreamEventTransformer {
                   break;
 
                 case _WebSocketMessageType.BINARY:
-                  _buffer.add(buffer.getRange(index, payload));
+                  _buffer.write(buffer.getRange(index, payload));
                   index += payload;
                   if (_remainingPayloadBytes == 0) {
                     _messageFrameEnd(sink);