Add relative path to test when creating generated multitest directory

tools/testing/dart/multitest.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.
 
 library multitest;
 
 import "dart:async";
 import "dart:io";
 
 import "path.dart";
@@ skipping 227 matching lines @@
     }
     file.writeAsStringSync(content);
   }
 
   // Each new test is a single String value in the Map tests.
   Map<String, String> tests = new Map<String, String>();
   Map<String, Set<String>> outcomes = new Map<String, Set<String>>();
   ExtractTestsFromMultitest(filePath, tests, outcomes);
 
   Path sourceDir = filePath.directoryPath;
-  Path targetDir = CreateMultitestDirectory(outputDir, suiteDir);
+  Path targetDir = createMultitestDirectory(outputDir, suiteDir, sourceDir);
   assert(targetDir != null);
 
   // Copy all the relative imports of the multitest.
   Set<String> importsToCopy = _findAllRelativeImports(filePath);
   List<Future> futureCopies = [];
   for (String relativeImport in importsToCopy) {
     Path importPath = new Path(relativeImport);
     // Make sure the target directory exists.
     Path importDir = importPath.directoryPath;
     if (!importDir.isEmpty) {
@@ skipping 29 matching lines @@
           isNegativeIfChecked: isNegativeIfChecked,
           hasCompileErrorIfChecked: hasCompileErrorIfChecked,
           hasStaticWarning: hasStaticWarning,
           multitestKey: key);
     }
 
     return null;
   });
 }
 
-Path CreateMultitestDirectory(String outputDir, Path suiteDir) {
-  Directory generatedTestDir = new Directory('$outputDir/generated_tests');
-  if (!new Directory(outputDir).existsSync()) {
-    new Directory(outputDir).createSync();
-  }
-  if (!generatedTestDir.existsSync()) {
-    generatedTestDir.createSync();
-  }
+String suiteNameFromPath(Path suiteDir) {
   var split = suiteDir.segments();
+  // co19 test suite is at tests/co19/src.
   if (split.last == 'src') {
-    // TODO(sigmund): remove this once all tests are migrated to use
-    // TestSuite.forDirectory.
     split.removeLast();
   }
-  String path = '${generatedTestDir.path}/${split.last}';
-  Directory dir = new Directory(path);
-  if (!dir.existsSync()) {
-    dir.createSync();
-  }
-  return new Path(new File(path).absolute.path);
+  return split.last;
 }
+
+Path createMultitestDirectory(String outputDir, Path suiteDir, Path sourceDir) {
+  Path relative = sourceDir.relativeTo(suiteDir);
+  Path path = new Path(outputDir).append('generated_tests')
+      .append(suiteNameFromPath(suiteDir)).join(relative);
+  TestUtils.mkdirRecursive(TestUtils.currentWorkingDirectory, path);
+  return new Path(new File(path.toNativePath()).absolute.path);
+}