Make RenderObject::style() return a const object

Source/core/editing/iterators/TextIterator.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov.
  *
  * 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
@@ skipping 817 matching lines @@
 
     // NOTE: We only do this for a select set of nodes, and fwiw WinIE appears
     // not to do this at all
     if (node->hasTagName(h1Tag)
         || node->hasTagName(h2Tag)
         || node->hasTagName(h3Tag)
         || node->hasTagName(h4Tag)
         || node->hasTagName(h5Tag)
         || node->hasTagName(h6Tag)
         || node->hasTagName(pTag)) {
-        LayoutStyle* style = r->style();
+        const LayoutStyle* style = r->style();
         if (style) {
             int bottomMargin = toRenderBox(r)->collapsedMarginAfter();
             int fontSize = style->fontDescription().computedPixelSize();
             if (bottomMargin * 2 >= fontSize)
                 return true;
         }
     }
 
     return false;
 }
@@ skipping 329 matching lines @@
     return createPlainText(it);
 }
 
 String plainText(const Position& start, const Position& end, TextIteratorBehaviorFlags behavior)
 {
     TextIterator it(start, end, behavior);
     return createPlainText(it);
 }
 
 }