Renaming dart:html library from 'html' to 'dart.html'

tools/dom/templates/html/impl/impl_CustomEvent.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.
 
 // WARNING: Do not edit - generated code.
 
-part of html;
+part of $LIBRARYNAME;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   factory $CLASSNAME(String type,
       {bool canBubble: true, bool cancelable: true, Object detail}) {
 
     final CustomEvent e = document.$dom_createEvent("CustomEvent");
     e.$dom_initCustomEvent(type, canBubble, cancelable, detail);
 
     return e;
   }
 $!MEMBERS
 }