Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/lib/src/system_cache.dart

Index: sdk/lib/_internal/pub_generated/lib/src/system_cache.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/system_cache.dart b/sdk/lib/_internal/pub_generated/lib/src/system_cache.dart
deleted file mode 100644
index 424585da3a091c116a287c7ee6f1d688cc82f0e8..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/system_cache.dart
+++ /dev/null
@@ -1,108 +0,0 @@
-// 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 pub.system_cache;
-
-import 'dart:async';
-import 'dart:io';
-
-import 'package:path/path.dart' as path;
-
-import 'io.dart';
-import 'io.dart' as io show createTempDir;
-import 'log.dart' as log;
-import 'package.dart';
-import 'source/cached.dart';
-import 'source/git.dart';
-import 'source/hosted.dart';
-import 'source/path.dart';
-import 'source.dart';
-import 'source_registry.dart';
-
-/// The system-wide cache of downloaded packages.
-///
-/// This cache contains all packages that are downloaded from the internet.
-/// Packages that are available locally (e.g. path dependencies) don't use this
-/// cache.
-class SystemCache {
-  /// The root directory where this package cache is located.
-  final String rootDir;
-
-  String get tempDir => path.join(rootDir, '_temp');
-
-  /// The sources from which to get packages.
-  final sources = new SourceRegistry();
-
-  static String defaultDir = (() {
-    if (Platform.environment.containsKey('PUB_CACHE')) {
-      return Platform.environment['PUB_CACHE'];
-    } else if (Platform.operatingSystem == 'windows') {
-      var appData = Platform.environment['APPDATA'];
-      return path.join(appData, 'Pub', 'Cache');
-    } else {
-      return '${Platform.environment['HOME']}/.pub-cache';
-    }
-  })();
-
-  /// Creates a new package cache which is backed by the given directory on the
-  /// user's file system.
-  SystemCache([String rootDir])
-      : rootDir = rootDir == null ? SystemCache.defaultDir : rootDir;
-
-  /// Creates a system cache and registers the standard set of sources.
-  ///
-  /// If [isOffline] is `true`, then the offline hosted source will be used.
-  /// Defaults to `false`.
-  factory SystemCache.withSources({String rootDir, bool isOffline: false}) {
-    var cache = new SystemCache(rootDir);
-    cache.register(new GitSource());
-
-    if (isOffline) {
-      cache.register(new OfflineHostedSource());
-    } else {
-      cache.register(new HostedSource());
-    }
-
-    cache.register(new PathSource());
-    cache.sources.setDefault('hosted');
-    return cache;
-  }
-
-  /// Registers a new source.
-  ///
-  /// This source must not have the same name as a source that's already been
-  /// registered.
-  void register(Source source) {
-    source.bind(this);
-    sources.register(source);
-  }
-
-  /// Determines if the system cache contains the package identified by [id].
-  Future<bool> contains(PackageId id) {
-    var source = sources[id.source];
-
-    if (source is! CachedSource) {
-      throw new ArgumentError("Package $id is not cacheable.");
-    }
-
-    return source.isInSystemCache(id);
-  }
-
-  /// Create a new temporary directory within the system cache.
-  ///
-  /// The system cache maintains its own temporary directory that it uses to
-  /// stage packages into while downloading. It uses this instead of the OS's
-  /// system temp directory to ensure that it's on the same volume as the pub
-  /// system cache so that it can move the directory from it.
-  String createTempDir() {
-    var temp = ensureDir(tempDir);
-    return io.createTempDir(temp, 'dir');
-  }
-
-  /// Deletes the system cache's internal temp directory.
-  void deleteTempDir() {
-    log.fine('Clean up system cache temp directory $tempDir.');
-    if (dirExists(tempDir)) deleteEntry(tempDir);
-  }
-}