Don't copy Int8Arrays when passing them in as lists of bytes and don't

sdk/lib/io/common.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.
 
 // Constants used when working with native ports.
 const int _SUCCESS_RESPONSE = 0;
 const int _ILLEGAL_ARGUMENT_RESPONSE = 1;
 const int _OSERROR_RESPONSE = 2;
 const int _FILE_CLOSED_RESPONSE = 3;
 
@@ skipping 50 matching lines @@
   List buffer;
   int offset;
 }
 
 // Ensure that the input List can be serialized through a native port.
 // Only builtin Lists can be serialized through. If user-defined Lists
 // get here, the contents is copied to a Uint8List. This has the added
 // benefit that it is faster to access from the C code as well.
 _BufferAndOffset _ensureFastAndSerializableBuffer(
     List buffer, int offset, int bytes) {
-  if (buffer is Uint8List || _BufferUtils._isBuiltinList(buffer)) {
+  if (buffer is Uint8List ||
+      buffer is Int8List ||
+      _BufferUtils._isBuiltinList(buffer)) {
     return new _BufferAndOffset(buffer, offset);
   }
   var newBuffer = new Uint8List(bytes);
   int j = offset;
   for (int i = 0; i < bytes; i++) {
     int value = buffer[j];
     if (value is! int) {
       throw new ArgumentError("List element is not an integer at index $j");
     }
     newBuffer[i] = value;
     j++;
   }
   return new _BufferAndOffset(newBuffer, 0);
 }
 
 
 // TODO(ager): The only reason for the class here is that
 // we cannot patch a top-level function.
 class _BufferUtils {
   // Check if a List is a builtin VM List type. Returns true
   // if the List is a builtin VM List type and false if it is
   // a user defined List type.
   external static bool _isBuiltinList(List buffer);
 }