Report hint on unmatched show and hide combinators.

tools/dom/templates/html/dartium/html_dartium.darttemplate

 // 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.
 
 // DO NOT EDIT
 // Auto-generated dart:html library.
 
 /**
  * HTML elements and other resources for web-based applications that need to
  * interact with the browser and the DOM (Document Object Model).
@@ skipping 15 matching lines @@
  * and run its built-in examples.
  *
  * * For even more examples, see
  * [Dart HTML5 Samples](https://github.com/dart-lang/dart-html5-samples)
  * on Github.
  */
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:_internal' hide Symbol, deprecated;
+import 'dart:_internal' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:indexed_db' show indexed_dbBlinkMap;
 import 'dart:indexed_db' show indexed_dbBlinkFunctionMap;
 import 'dart:isolate';
 import 'dart:js' as js;
 import "dart:convert";
 import 'dart:math';
 // TODO(vsm): Remove this when we can do the proper checking in
 // native code for custom elements.
@@ skipping 379 matching lines @@
   var frozen_nodes = new _FrozenElementList._wrap(nodes);
   frozen_nodes.dartClass_instance = jso_nodes;
   return frozen_nodes;
 }
 $else
 unwrap_jso(dartClass_instance) => dartClass_instance;
 wrap_jso(jsObject) => jsObject;
 wrap_jso_list(jso_nodes) => jso_nodes;
 make_dart_rectangle(r) => r;
 $endif