Replace defer() with Future.of in pub.

utils/pub/utils.dart

Index: utils/pub/utils.dart
diff --git a/utils/pub/utils.dart b/utils/pub/utils.dart
index 7460891490da08e5f2206f0cf4852461e54cfe63..cb316cbebbb763b2fcd0724b029ec0e77189e62b 100644
--- a/utils/pub/utils.dart
+++ b/utils/pub/utils.dart
@@ -145,18 +145,6 @@ String sha1(String source) {
   return CryptoUtils.bytesToHex(sha.close());
 }
 
-// TODO(nweiz): Use Future.of instead of this wherever we don't actually need
-// asynchrony.
-/// Invokes the given callback asynchronously. Returns a [Future] that completes
-/// to the result of [callback].
-///
-/// This is also used to wrap synchronous code that may thrown an exception to
-/// ensure that methods that have both sync and async code only report errors
-/// asynchronously.
-Future defer(callback()) {
-  return new Future.immediate(null).then((_) => callback());
-}
-
 /// Returns a [Future] that completes in [milliseconds].
 Future sleep(int milliseconds) {
   var completer = new Completer();