Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/barback/lib/src/asset/asset.dart

+// Copyright (c) 2013, 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 barback.asset.asset;
+
+import 'dart:async';
+import 'dart:io';
+import 'dart:convert';
+
+import 'asset_id.dart';
+import 'internal_asset.dart';
+
+/// A blob of content.
+///
+/// Assets may come from the file system, or as the output of a [Transformer].
+/// They are identified by [AssetId].
+///
+/// Custom implementations of [Asset] are not currently supported.
+abstract class Asset {
+  /// The ID for this asset.
+  final AssetId id;
+
+  factory Asset.fromBytes(AssetId id, List<int> bytes) =>
+      new BinaryAsset(id, bytes);
+
+  factory Asset.fromFile(AssetId id, File file) =>
+      new FileAsset(id, file.path);
+
+  factory Asset.fromString(AssetId id, String content) =>
+      new StringAsset(id, content);
+
+  factory Asset.fromPath(AssetId id, String path) =>
+      new FileAsset(id, path);
+
+  factory Asset.fromStream(AssetId id, Stream<List<int>> stream) =>
+      new StreamAsset(id, stream);
+
+  /// Returns the contents of the asset as a string.
+  ///
+  /// If the asset was created from a [String] the original string is always
+  /// returned and [encoding] is ignored. Otherwise, the binary data of the
+  /// asset is decoded using [encoding], which defaults to [UTF8].
+  Future<String> readAsString({Encoding encoding});
+
+  /// Streams the binary contents of the asset.
+  ///
+  /// If the asset was created from a [String], this returns its UTF-8 encoding.
+  Stream<List<int>> read();
+}