- Apply review comments from https://codereview.chromium.org/232223004/

sdk/lib/io/link.dart

Index: sdk/lib/io/link.dart
===================================================================
--- sdk/lib/io/link.dart	(revision 34928)
+++ sdk/lib/io/link.dart	(working copy)
@@ -163,7 +163,7 @@
   FileStat statSync() => FileStat.statSync(path);
 
   Future<Link> create(String target, {bool recursive: false}) {
-    if (Platform.operatingSystem == 'windows') {
+    if (Platform.isWindows) {
       target = _makeWindowsLinkTarget(target);
     }
     var result = recursive ? parent.create(recursive: true)
@@ -183,7 +183,7 @@
     if (recursive) {
       parent.createSync(recursive: true);
     }
-    if (Platform.operatingSystem == 'windows') {
+    if (Platform.isWindows) {
       target = _makeWindowsLinkTarget(target);
     }
     var result = _File._createLink(path, target);