Add check to InlineFlowBox::computeLogicalBoxHeights

third_party/WebKit/Source/core/layout/line/InlineFlowBox.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc.
  *               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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 570 matching lines @@
   // scratch space.
   //
   // Because a box can be positioned such that it ends up fully above or fully
   // below the root line box, we only consider it to affect the maxAscent and
   // maxDescent values if some part of the box (EXCLUDING leading) is above (for
   // ascent) or below (for descent) the root box's baseline.
   bool affectsAscent = false;
   bool affectsDescent = false;
   bool checkChildren = !descendantsHaveSameLineHeightAndBaseline();
 
+  DCHECK(rootBox);
+  if (!rootBox)
+    return;
+
   if (isRootInlineBox()) {
     // Examine our root box.
     int ascent = 0;
     int descent = 0;
     rootBox->ascentAndDescentForBox(rootBox, textBoxDataMap, ascent, descent,
                                     affectsAscent, affectsDescent);
     if (noQuirksMode || hasTextChildren() ||
         (!checkChildren && hasTextDescendants())) {
       if (maxAscent < ascent || !setMaxAscent) {
         maxAscent = ascent;
@@ skipping 1041 matching lines @@
     ASSERT(child->prevOnLine() == prev);
     prev = child;
   }
   ASSERT(prev == m_lastChild);
 #endif
 }
 
 #endif
 
 }  // namespace blink