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

mojo/public/dart/third_party/barback/test/transformer/declaring_aggregate_many_to_many.dart

Index: mojo/public/dart/third_party/barback/test/transformer/declaring_aggregate_many_to_many.dart
diff --git a/mojo/public/dart/third_party/barback/test/transformer/declaring_aggregate_many_to_many.dart b/mojo/public/dart/third_party/barback/test/transformer/declaring_aggregate_many_to_many.dart
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+// 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 barback.test.transformer.declaring_aggregate_many_to_many;
+
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+
+import 'aggregate_many_to_many.dart';
+
+/// Like [AggregateManyToManyTransformer], but declares its assets ahead of
+/// time.
+class DeclaringAggregateManyToManyTransformer
+    extends AggregateManyToManyTransformer
+    implements DeclaringAggregateTransformer {
+  DeclaringAggregateManyToManyTransformer(String extension)
+      : super(extension);
+
+  Future declareOutputs(DeclaringAggregateTransform transform) =>
+      transform.primaryIds.asyncMap(transform.declareOutput).toList();
+}