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

tests/standalone/src/FileInputStreamTest.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.
 // Testing file input stream, VM-only, standalone test.
 
+#import("dart:io");
+
 // Helper method to be able to run the test from the runtime
 // directory, or the top directory.
 String getFilename(String path) =>
     new File(path).existsSync() ? path : '../' + path;
 
 void testStringInputStreamSync() {
   String fileName = getFilename("tests/standalone/src/readuntil_test.dat");
   // File contains "Hello Dart\nwassup!\n"
   File file = new File(fileName);
   StringInputStream x = new StringInputStream(file.openInputStream());
@@ skipping 65 matching lines @@
 main() {
   testStringInputStreamSync();
   testInputStreamAsync();
   // Check the length of these files as both are text files where one
   // is without a terminating line separator which can easily be added
   // back if accidentally opened in a text editor.
   testStringInputStreamAsync("readline_test1.dat", 111);
   testStringInputStreamAsync("readline_test2.dat", 114);
   testChunkedInputStream();
 }