Remove calls to [new Future] work around issue 11911.

sdk/lib/_internal/pub/lib/src/source/hosted.dart

Index: sdk/lib/_internal/pub/lib/src/source/hosted.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source/hosted.dart b/sdk/lib/_internal/pub/lib/src/source/hosted.dart
index aec150c888026320a7fa567d5c772641c84cbf86..070f5749f65a1f13f9e2055bb0c2048b780882b8 100644
--- a/sdk/lib/_internal/pub/lib/src/source/hosted.dart
+++ b/sdk/lib/_internal/pub/lib/src/source/hosted.dart
@@ -181,7 +181,7 @@ class HostedSource extends Source {
 class OfflineHostedSource extends HostedSource {
   /// Gets the list of all versions of [name] that are in the system cache.
   Future<List<Version>> getVersions(String name, description) {
-    return new Future(() {
+    return newFuture(() {
       var parsed = _parseDescription(description);
       var server = parsed.last;
       log.io("Finding versions of $name in "