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

tests/standalone/src/TestRunnerTest.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.
 
 #library("TestRunnerTest");
 
+#import("dart:io");
 #import("../../../tools/testing/dart/test_runner.dart");
 #import("../../../tools/testing/dart/status_file_parser.dart");
 #source("ProcessTestUtil.dart");
 
 class TestController {
   static final int numTests = 4;
   static int numCompletedTests = 0;
 
   // Used as TestCase.completedCallback.
   static processCompletedTest(TestCase testCase) {
@@ skipping 50 matching lines @@
                                   getProcessTestFileName(),
                                   const ["0", "0", "1", "1"],
                                   configuration,
                                   TestController.processCompletedTest,
                                   new Set<String>.from([CRASH]))).start();
   Expect.equals(4, TestController.numTests);
   // Throw must be from body of start() function for this test to work.
   Expect.throws(new RunningProcess(MakeTestCase("PassTest", [SKIP])).start);
 }