Escape slash since it helps to end an HTML entity.

sdk/lib/convert/html_escape.dart

 // 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.
 
 part of dart.convert;
 
 // TODO(floitsch) - Document - Issue 13097
 const HTML_ESCAPE = const HtmlEscape();
 
 class HtmlEscapeMode {
   final String _name;
   final bool escapeLtGt;
   final bool escapeQuot;
   final bool escapeApos;
+  final bool escapeSlash;
 
   // TODO(floitsch) - Document - Issue 13097
   static const HtmlEscapeMode UNKNOWN =
-    const HtmlEscapeMode._('unknown', true, true, true);
+    const HtmlEscapeMode._('unknown', true, true, true, true);
 
   // TODO(floitsch) - Document - Issue 13097
   static const HtmlEscapeMode ATTRIBUTE =
-    const HtmlEscapeMode._('attribute', false, true, false);
+    const HtmlEscapeMode._('attribute', false, true, false, false);
 
   // TODO(floitsch) - Document - Issue 13097
   static const HtmlEscapeMode ELEMENT =
-    const HtmlEscapeMode._('element', true, false, false);
+    const HtmlEscapeMode._('element', true, false, false, true);
 
   // TODO(floitsch) - Document - Issue 13097
   const HtmlEscapeMode._(this._name, this.escapeLtGt, this.escapeQuot,
-    this.escapeApos);
+    this.escapeApos, this.escapeSlash);
 
   String toString() => _name;
 }
 
   // TODO(floitsch) - Document - Issue 13097
 class HtmlEscape extends Converter<String, String> {
 
   // TODO(floitsch) - Document - Issue 13097
   final HtmlEscapeMode mode;
 
   // TODO(floitsch) - Document - Issue 13097
   const HtmlEscape([this.mode = HtmlEscapeMode.UNKNOWN]);
 
   String convert(String text) {
     var val = _convert(text, 0, text.length);
     return val == null ? text : val;
   }
 
   String _convert(String text, int start, int end) {
     StringBuffer result = null;
     for (int i = start; i < end; i++) {
       var ch = text[i];
       String replace = null;
       switch (ch) {
         case '&': replace = '&amp;'; break;
         case '\u00A0'/*NO-BREAK SPACE*/: replace = '&nbsp;'; break;
         case '"': if (mode.escapeQuot) replace = '&quot;'; break;
-        case "'": if (mode.escapeApos) replace = '&apos;'; break;
+        case "'": if (mode.escapeApos) replace = '&#x27;'; break;
         case '<': if (mode.escapeLtGt) replace = '&lt;'; break;
         case '>': if (mode.escapeLtGt) replace = '&gt;'; break;
+        case '/': if (mode.escapeSlash) replace = '&#x2F;'; break;
       }
       if (replace != null) {
         if (result == null) result = new StringBuffer(text.substring(start, i));
         result.write(replace);
       } else if (result != null) {
         result.write(ch);
       }
     }
 
     return result != null ? result.toString() : null;
@@ skipping 20 matching lines @@
     if(val == null) {
       _sink.addSlice(chunk, start, end, isLast);
     } else {
       _sink.add(val);
       if (isLast) _sink.close();
     }
   }
 
   void close() => _sink.close();
 }