Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/path/src/path_exception.dart

Index: observatory_pub_packages/path/src/path_exception.dart
===================================================================
--- observatory_pub_packages/path/src/path_exception.dart	(revision 0)
+++ observatory_pub_packages/path/src/path_exception.dart	(working copy)
@@ -0,0 +1,15 @@
+// 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.path_exception;
+
+/// An exception class that's thrown when a path operation is unable to be
+/// computed accurately.
+class PathException implements Exception {
+  String message;
+
+  PathException(this.message);
+
+  String toString() => "PathException: $message";
+}