Remove need to instantiate Platform and make methods static.

tools/testing/dart/multitest.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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:io");
 #import("test_suite.dart");
 
 // Multitests are Dart test scripts containing lines of the form
 // " [some dart code] /// [key]: [error type]"
@@ skipping 136 matching lines @@
         .map((s) => s.trim());
     return annotation;
   }
 }
 
 // Find all relative imports and copy them into the dir that contains
 // the generated tests.
 Set<String> _findAllRelativeImports(String topLibrary) {
   Set<String> toSearch = new Set<String>.from([topLibrary]);
   Set<String> foundImports = new HashSet<String>();
-  String pathSep = new Platform().pathSeparator();
+  String pathSep = Platform.pathSeparator();
   int end = topLibrary.lastIndexOf(pathSep);
   String libraryDir = topLibrary.substring(0, end);
 
   // Matches #import( or #source( followed by " or ' followed by anything
   // except dart: or /, at the beginning of a line.
   RegExp relativeImportRegExp =
       const RegExp('^#(import|source)[(]["\'](?!(dart:|/))([^"\']*)["\']');
   while (!toSearch.isEmpty()) {
     var thisPass = toSearch;
     toSearch = new HashSet<String>();
@@ skipping 33 matching lines @@
                                   bool hasRuntimeErrors,
                                   Set<String> multitestOutcome]),
                  Function multitestDone) {
   // 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(filename, tests, outcomes);
 
   String directory = CreateMultitestDirectory(outputDir, testDir);
   Expect.isNotNull(directory);
-  String pathSep = new Platform().pathSeparator();
+  String pathSep = Platform.pathSeparator();
   int start = filename.lastIndexOf(pathSep) + 1;
   int end = filename.indexOf('.dart', start);
   String baseFilename = filename.substring(start, end);
   String sourceDirectory = filename.substring(0, start - 1);
   Set<String> importsToCopy = _findAllRelativeImports(filename);
   Directory destDir = new Directory("directory");
   for (String import in importsToCopy) {
     File source = new File('$sourceDirectory/$import');
     var dest = new File('$directory/$import');
     var basenameStart = import.lastIndexOf('/');
@@ skipping 42 matching lines @@
   var split = testDir.split('/');
   var lastComponent = split.removeLast();
   Expect.isTrue(lastComponent == 'src');
   String path = '${generatedTestDir.path}/${split.last()}';
   Directory dir = new Directory(path);
   if (!dir.existsSync()) {
     dir.createSync();
   }
   return path;
 }