Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/utf/src/constants.dart

Index: observatory_pub_packages/utf/src/constants.dart
===================================================================
--- observatory_pub_packages/utf/src/constants.dart	(revision 0)
+++ observatory_pub_packages/utf/src/constants.dart	(working copy)
@@ -0,0 +1,25 @@
+// Copyright (c) 2012, 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 utf.constants;
+
+/**
+ * Invalid codepoints or encodings may be substituted with the value U+fffd.
+ */
+const int UNICODE_REPLACEMENT_CHARACTER_CODEPOINT = 0xfffd;
+const int UNICODE_BOM = 0xfeff;
+const int UNICODE_UTF_BOM_LO = 0xff;
+const int UNICODE_UTF_BOM_HI = 0xfe;
+
+const int UNICODE_BYTE_ZERO_MASK = 0xff;
+const int UNICODE_BYTE_ONE_MASK = 0xff00;
+const int UNICODE_VALID_RANGE_MAX = 0x10ffff;
+const int UNICODE_PLANE_ONE_MAX = 0xffff;
+const int UNICODE_UTF16_RESERVED_LO = 0xd800;
+const int UNICODE_UTF16_RESERVED_HI = 0xdfff;
+const int UNICODE_UTF16_OFFSET = 0x10000;
+const int UNICODE_UTF16_SURROGATE_UNIT_0_BASE = 0xd800;
+const int UNICODE_UTF16_SURROGATE_UNIT_1_BASE = 0xdc00;
+const int UNICODE_UTF16_HI_MASK = 0xffc00;
+const int UNICODE_UTF16_LO_MASK = 0x3ff;