Big merge from experimental to bleeding edge.

utils/pub/validator/lib.dart

Index: utils/pub/validator/lib.dart
diff --git a/utils/pub/validator/lib.dart b/utils/pub/validator/lib.dart
index b0dfbe5e51c0b70e1d287c7835586202815961fb..6afeb88fb0e5a0b5556ab4448bd6942cb0a18c47 100644
--- a/utils/pub/validator/lib.dart
+++ b/utils/pub/validator/lib.dart
@@ -29,8 +29,8 @@ class LibValidator extends Validator {
         return new Future.immediate(null);
       }
 
-      return listDir(libDir).transform((files) {
-        files = files.map((file) => relativeTo(file, libDir));
+      return listDir(libDir).then((files) {
+        files = files.mappedBy((file) => relativeTo(file, libDir)).toList();
         if (files.isEmpty) {
           errors.add('You must have a non-empty "lib" directory.\n'
               "Without that, users cannot import any code from your package.");