Update corelib/ and lib/ to use the new try-catch syntax.

lib/html/src/XMLElementWrappingImplementation.dart

 // 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.
 
 class _XMLClassSet extends _CssClassSet {
   _XMLClassSet(element) : super(element);
 
   String _className() {
     final classStr = _element.getAttribute('class');
     return classStr == null ? '' : classStr;
@@ skipping 139 matching lines @@
     if (value) {
       attributes['hidden'] = '';
     } else {
       attributes.remove('hidden');
     }
   }
 
   int get tabIndex() {
     try {
       return Math.parseInt(_attr('tabIndex'));
-    } catch (FormatException e) {
+    } on FormatException catch (e) {
       return 0;
     }
   }
 
   void set tabIndex(int value) { attributes['tabIndex'] = value.toString(); }
 
   String get id() => _attr('id');
 
   void set id(String value) { attributes['id'] = value; }
 
@@ skipping 11 matching lines @@
 
   void set lang(String value) { attributes['lang'] = value; }
 
   String get dir() => _attr('dir');
 
   void set dir(String value) { attributes['dir'] = value; }
 
   String _attr(String name, [String def = '']) =>
     attributes.containsKey(name) ? attributes[name] : def;
 }