Fix a couple of minor issues and try to resolve #2740.

utils/pub/package.dart

Index: utils/pub/package.dart
diff --git a/utils/pub/package.dart b/utils/pub/package.dart
index 8e621371591ac08f04df69a7343c5c017b5b35fc..7d707fd98240e03e580137cd84825329dea2d21b 100644
--- a/utils/pub/package.dart
+++ b/utils/pub/package.dart
@@ -70,7 +70,7 @@ class Package implements Hashable {
 
       // Recurse into its dependencies.
       pendingAsyncCalls++;
-      package.loadDependencies().then((dependencies) {
+      package.loadDependencies(cache).then((dependencies) {
         dependencies.forEach(walkPackage);
         pendingAsyncCalls--;
         if (pendingAsyncCalls == 0) completer.complete(packages);