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

mojo/public/dart/third_party/path/test/utils.dart

Index: mojo/public/dart/third_party/path/test/utils.dart
diff --git a/mojo/public/dart/third_party/path/test/utils.dart b/mojo/public/dart/third_party/path/test/utils.dart
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index 0000000000000000000000000000000000000000..1730798f09479c06275a190bcce69f0e355daf04
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+++ b/mojo/public/dart/third_party/path/test/utils.dart
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+// 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 path.test.utils;
+
+import "package:unittest/unittest.dart";
+import "package:path/path.dart" as path;
+
+/// A matcher for a closure that throws a [path.PathException].
+final throwsPathException = throwsA(new isInstanceOf<path.PathException>());