Changed @domName annotation in comment to full fledge @DomName annotation.

tools/dom/templates/html/impl/impl_MutationObserver.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.
 
 part of html;
-
-/// @domName $DOMNAME
+$ANNOTATIONS
 @SupportedBrowser(SupportedBrowser.CHROME)
 @SupportedBrowser(SupportedBrowser.FIREFOX)
 @SupportedBrowser(SupportedBrowser.SAFARI)
 @Experimental()
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 $!MEMBERS
   /**
    * Checks to see if the mutation observer API is supported on the current
    * platform.
    */
@@ skipping 82 matching lines @@
     // Dummy statement to mark types as instantiated.
     JS('MutationObserver|MutationRecord', '0');
 
     return JS('MutationObserver',
         'new(window.MutationObserver||window.WebKitMutationObserver||'
         'window.MozMutationObserver)(#)',
         convertDartClosureToJS(callback, 2));
   }
 $endif
 }