Remove deprecated packages from the repo

pkg/custom_element/lib/src/custom_tag_name.dart

Index: pkg/custom_element/lib/src/custom_tag_name.dart
diff --git a/pkg/custom_element/lib/src/custom_tag_name.dart b/pkg/custom_element/lib/src/custom_tag_name.dart
deleted file mode 100644
index 72d915039db8b5d8d046de806898d554a337dfec..0000000000000000000000000000000000000000
--- a/pkg/custom_element/lib/src/custom_tag_name.dart
+++ /dev/null
@@ -1,27 +0,0 @@
-// 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 custom_element.src.custom_tag_name;
-
-/**
- * Returns true if this is a valid custom element name. See:
- * <https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/index.html#dfn-custom-element-name>
- */
-bool isCustomTag(String name) {
-  if (!name.contains('-')) return false;
-
-  // These names have meaning in SVG or MathML, so they aren't allowed as custom
-  // tags.
-  var invalidNames = const {
-    'annotation-xml': '',
-    'color-profile': '',
-    'font-face': '',
-    'font-face-src': '',
-    'font-face-uri': '',
-    'font-face-format': '',
-    'font-face-name': '',
-    'missing-glyph': '',
-  };
-  return !invalidNames.containsKey(name);
-}