Fix a use-after-free in spellcheck client

Source/core/editing/SpellChecker.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 71 matching lines @@
 
 const TextCheckingRequestData& SpellCheckRequest::data() const
 {
     return m_requestData;
 }
 
 void SpellCheckRequest::didSucceed(const Vector<TextCheckingResult>& results)
 {
     if (!m_checker)
         return;
-    m_checker->didCheckSucceed(m_requestData.sequence(), results);
+    SpellChecker* checker = m_checker;
     m_checker = 0;
+    checker->didCheckSucceed(m_requestData.sequence(), results);
 }
 
 void SpellCheckRequest::didCancel()
 {
     if (!m_checker)
         return;
-    m_checker->didCheckCancel(m_requestData.sequence());
+    SpellChecker* checker = m_checker;
     m_checker = 0;
+    checker->didCheckCancel(m_requestData.sequence());
 }
 
 void SpellCheckRequest::setCheckerAndSequence(SpellChecker* requester, int sequence)
 {
     ASSERT(!m_checker);
     ASSERT(m_requestData.sequence() == unrequestedTextCheckingSequence);
     m_checker = requester;
     m_requestData.m_sequence = sequence;
 }
 
@@ skipping 141 matching lines @@
     didCheck(sequence, results);
 }
 
 void SpellChecker::didCheckCancel(int sequence)
 {
     Vector<TextCheckingResult> results;
     didCheck(sequence, results);
 }
 
 } // namespace WebCore