Fix various warnings and errors in html_diff and its annotations.

client/html/src/LoseContextWrappingImplementation.dart

 // Copyright (c) 2011, 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.
-
+/** @domName WebGLLoseContext */
 class LoseContextWrappingImplementation extends DOMWrapperBase implements LoseContext {
   LoseContextWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
   void loseContext() {
     _ptr.loseContext();
     return;
   }
 
   void restoreContext() {
     _ptr.restoreContext();
     return;
   }
 }