Fix a couple lingering bugs from the last snapshot CL.

sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart

Index: sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart b/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
index 5956aeabacf785dc1a7623eb1d6b013db11437e4..18bf853d4262d8f5e6644cfd32df034ab2f914b1 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
@@ -55,8 +55,8 @@ Future loadAllTransformers(AssetEnvironment environment,
   // Add a rewrite transformer for each package, so that we can resolve
   // "package:" imports while loading transformers.
   var rewrite = new RewriteImportTransformer();
-  for (var package in environment.graph.packages.values) {
-    environment.barback.updateTransformers(package.name, [[rewrite]]);
+  for (var package in environment.packages) {
+    environment.barback.updateTransformers(package, [[rewrite]]);
   }
   environment.barback.updateTransformers(r'$pub', [[rewrite]]);