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

mojo/public/dart/third_party/analyzer/lib/source/package_map_provider.dart

+// Copyright (c) 2014, 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.package_map_provider;
+
+import 'package:analyzer/file_system/file_system.dart';
+
+/**
+ * Data structure output by PackageMapProvider.  This contains both the package
+ * map and dependency information.
+ */
+class PackageMapInfo {
+  /**
+   * The package map itself.  This is a map from package name to a list of
+   * the folders containing source code for the package.
+   *
+   * `null` if an error occurred.
+   */
+  Map<String, List<Folder>> packageMap;
+
+  /**
+   * Dependency information.  This is a set of the paths which were consulted
+   * in order to generate the package map.  If any of these files is
+   * modified, the package map will need to be regenerated.
+   */
+  Set<String> dependencies;
+
+  PackageMapInfo(this.packageMap, this.dependencies);
+}
+
+/**
+ * A PackageMapProvider is an entity capable of determining the mapping from
+ * package name to source directory for a given folder.
+ */
+abstract class PackageMapProvider {
+  /**
+   * Compute a package map for the given folder, if possible.
+   *
+   * If a package map can't be computed (e.g. because an error occurred), a
+   * [PackageMapInfo] will still be returned, but its packageMap will be null.
+   */
+  PackageMapInfo computePackageMap(Folder folder);
+}