Get rid of old redundant methods in io.dart.

utils/pub/source.dart

Index: utils/pub/source.dart
diff --git a/utils/pub/source.dart b/utils/pub/source.dart
index 777c1a0222fc8f8ffbd1e4e9229cc5ca77009279..5f79e2986bfd8059c11b66503fe06119194daa64 100644
--- a/utils/pub/source.dart
+++ b/utils/pub/source.dart
@@ -5,6 +5,9 @@
 library source;
 
 import 'dart:async';
+
+import '../../pkg/path/lib/path.dart' as path;
+
 import 'io.dart';
 import 'package.dart';
 import 'pubspec.dart';
@@ -105,15 +108,15 @@ abstract class Source {
   ///
   /// By default, this uses [systemCacheDirectory] and [install].
   Future<Package> installToSystemCache(PackageId id) {
-    var path;
+    var packageDir;
     return systemCacheDirectory(id).then((p) {
-      path = p;
-      if (dirExists(path)) return true;
-      ensureDir(dirname(path));
-      return install(id, path);
+      packageDir = p;
+      if (dirExists(packageDir)) return true;
+      ensureDir(path.dirname(packageDir));
+      return install(id, packageDir);
     }).then((found) {
       if (!found) throw 'Package $id not found.';
-      return new Package.load(id.name, path, systemCache.sources);
+      return new Package.load(id.name, packageDir, systemCache.sources);
     });
   }