make sure fields are initialized in OverflowEventDispatcher

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 99 matching lines @@
 
 static bool gColumnFlowSplitEnabled = true;
 
 // This class helps dispatching the 'overflow' event on layout change. overflow can be set on RenderBoxes, yet the existing code
 // only works on RenderBlocks. If this changes, this class should be shared with other RenderBoxes.
 class OverflowEventDispatcher {
     WTF_MAKE_NONCOPYABLE(OverflowEventDispatcher);
 public:
     OverflowEventDispatcher(const RenderBlock* block)
         : m_block(block)
+        , m_hadHorizontalLayoutOverflow(false)
+        , m_hadVerticalLayoutOverflow(false)
     {
         m_shouldDispatchEvent = !m_block->isAnonymous() && m_block->hasOverflowClip() && m_block->document().hasListenerType(Document::OVERFLOWCHANGED_LISTENER);
         if (m_shouldDispatchEvent) {
             m_hadHorizontalLayoutOverflow = m_block->hasHorizontalLayoutOverflow();
             m_hadVerticalLayoutOverflow = m_block->hasVerticalLayoutOverflow();
         }
     }
 
     ~OverflowEventDispatcher()
     {
@@ skipping 4895 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace WebCore