Fix recursive directory-deletion of top-level files/links.

BUG=

Review URL: https://codereview.chromium.org//13771010

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@21060 260f80e4-7a28-3924-810f-c04153c831b5

lib/src/io.dart

@@ -188,12 +188,7 @@ bool dirExists(String dir) => new Directory(dir).existsSync();
 void deleteEntry(String path) {
   if (linkExists(path)) {
     log.io("Deleting link $path.");
-    if (Platform.operatingSystem == 'windows') {
-      // TODO(nweiz): remove this when issue 9278 is fixed.
-      new Directory(path).deleteSync();
-    } else {
-      new Link(path).deleteSync();
-    }
+    new Link(path).deleteSync();
   } else if (dirExists(path)) {
     log.io("Deleting directory $path.");
     new Directory(path).deleteSync(recursive: true);