Use ByteArray's native for Socket and File.

runtime/bin/socket_impl.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.
 
 
 class _SocketBase {
   // Bit flags used when communicating between the eventhandler and
   // dart code. The EVENT flags are used to indicate events of
   // interest when sending a message from dart code to the
   // eventhandler. When receiving a message from the eventhandler the
@@ skipping 288 matching lines @@
       }
       if (offset < 0) {
         throw new IndexOutOfRangeException(offset);
       }
       if (bytes < 0) {
         throw new IndexOutOfRangeException(bytes);
       }
       if ((offset + bytes) > buffer.length) {
         throw new IndexOutOfRangeException(offset + bytes);
       }
-      // When using the Dart C API access to ObjectArray by index is
+      // When using the Dart C API to access raw data, using a ByteArray is
       // currently much faster. This function will make a copy of the
-      // supplied List to an ObjectArray if it isn't already.
-      ObjectArray outBuffer;
+      // supplied List to a ByteArray if it isn't already.
+      List outBuffer;
       int outOffset = offset;
-      if (buffer is ObjectArray) {
+      if (buffer is ByteArray || buffer is ObjectArray) {
         outBuffer = buffer;
       } else {
-        outBuffer = new ObjectArray(bytes);
+        outBuffer = new ByteArray(bytes);
         outOffset = 0;
         int j = offset;
         for (int i = 0; i < bytes; i++) {
-          outBuffer[i] = buffer[j];
+          int value = buffer[j];
+          if (value is! int) {
+            throw new FileIOException(
+                "List element is not an integer at index $j");
+          }
+          outBuffer[i] = value;
           j++;
         }
       }
       var bytes_written = _writeList(outBuffer, outOffset, bytes);
       if (bytes_written < 0) {
         // If writing fails we return 0 as the number of bytes and
         // report the error on the error handler.
         bytes_written = 0;
         _reportError();
       }
@@ skipping 123 matching lines @@
   bool _seenFirstOutEvent = false;
   bool _closedRead = false;
   bool _closedWrite = false;
   bool _pipe = false;
   Function _clientConnectHandler;
   Function _clientWriteHandler;
   SocketInputStream _inputStream;
   SocketOutputStream _outputStream;
 }