Split dart:builtin into dart:builtin and dart:io.

tests/standalone/src/ChunkedStreamTest.dart

 // Copyright (c) 2011, 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.
 
+#import("dart:io");
+
 void test1() {
   void testWithChunkSize(var data, int chunkSize, Function testDone) {
     InputStream s = new ListInputStream(data);
     ChunkedInputStream stream = new ChunkedInputStream(s);
     int chunkCount = 0;
     int byteCount = 0;
     void chunkData() {
       List<int> chunk = stream.read();
       if (byteCount + chunkSize < data.length) {
         Expect.equals(chunkSize, chunk.length);
@@ skipping 111 matching lines @@
   s.write([4, 5, 6]);  // 7 bytes written to stream.
 
   donePort.receive((x,y) => donePort.close());
 }
 
 
 main() {
   test1();
   test2();
 }