Get rid of old redundant methods in io.dart.

utils/pub/source.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.
 
 library source;
 
 import 'dart:async';
+
+import '../../pkg/path/lib/path.dart' as path;
+
 import 'io.dart';
 import 'package.dart';
 import 'pubspec.dart';
 import 'system_cache.dart';
 import 'utils.dart';
 import 'version.dart';
 
 /// A source from which to install packages.
 ///
 /// Each source has many packages that it looks up using [PackageId]s. The
@@ skipping 80 matching lines @@
   Future<bool> install(PackageId id, String path) {
     throw "Either install or installToSystemCache must be implemented for "
         "source $name.";
   }
 
   /// Installs the package identified by [id] to the system cache. This is only
   /// called for sources with [shouldCache] set to true.
   ///
   /// 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);
     });
   }
 
   /// Returns the directory in the system cache that the package identified by
   /// [id] should be installed to. This should return a path to a subdirectory
   /// of [systemCacheRoot].
   ///
   /// This doesn't need to be implemented if [shouldCache] is false.
   Future<String> systemCacheDirectory(PackageId id) {
     return new Future.immediateError(
@@ skipping 36 matching lines @@
   /// according to [validateDescription], although it must still be serializable
   /// to JSON and YAML. It must also be equal to [id] according to
   /// [descriptionsEqual].
   ///
   /// By default, this just returns [id].
   Future<PackageId> resolveId(PackageId id) => new Future.immediate(id);
 
   /// Returns the source's name.
   String toString() => name;
 }