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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : /*
       8             :  * nsStubMutationObserver is an implementation of the nsIMutationObserver
       9             :  * interface (except for the methods on nsISupports) that is intended to be
      10             :  * used as a base class within the content/layout library.  All methods do
      11             :  * nothing.
      12             :  */
      13             : 
      14             : #ifndef nsStubMutationObserver_h_
      15             : #define nsStubMutationObserver_h_
      16             : 
      17             : #include "nsIMutationObserver.h"
      18             : 
      19             : /**
      20             :  * There are two advantages to inheriting from nsStubMutationObserver
      21             :  * rather than directly from nsIMutationObserver:
      22             :  *  1. smaller compiled code size (since there's no need for the code
      23             :  *     for the empty virtual function implementations for every
      24             :  *     nsIMutationObserver implementation)
      25             :  *  2. the performance of document's loop over observers benefits from
      26             :  *     the fact that more of the functions called are the same (which
      27             :  *     can reduce instruction cache misses and perhaps improve branch
      28             :  *     prediction)
      29             :  */
      30         209 : class nsStubMutationObserver : public nsIMutationObserver {
      31             : public:
      32             :   NS_DECL_NSIMUTATIONOBSERVER
      33             : };
      34             : 
      35             : #endif /* !defined(nsStubMutationObserver_h_) */