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

utils/pub/package.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * A named, versioned, unit of code and resource reuse.
  */
 class Package implements Hashable {
   /**
    * Loads the package whose root directory is [packageDir].
@@ skipping 52 matching lines @@
 
     walkPackage(Package package) {
       // Skip packages we've already traversed.
       if (packages.contains(package)) return;
 
       // Add the package.
       packages.add(package);
 
       // Recurse into its dependencies.
       pendingAsyncCalls++;
-      package.loadDependencies().then((dependencies) {
+      package.loadDependencies(cache).then((dependencies) {
         dependencies.forEach(walkPackage);
         pendingAsyncCalls--;
         if (pendingAsyncCalls == 0) completer.complete(packages);
       });
     }
 
     walkPackage(this);
 
     return completer.future;
   }
@@ skipping 49 matching lines @@
         completer.completeException(
             'The pubspec dependencies must be a list of package names.');
       }
 
       completer.complete(dependencies);
     });
 
     return completer.future;
   }
 }