Make RenderObject::style() return a const object

Source/core/paint/ViewPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/ViewPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/paint/BlockPainter.h"
 #include "core/paint/GraphicsContextAnnotator.h"
@@ skipping 24 matching lines @@
         paintInfo.context->fillRect(paintRect, m_renderView.frameView()->baseBackgroundColor());
     }
 
     m_renderView.paintObject(paintInfo, paintOffset);
     BlockPainter(m_renderView).paintOverflowControlsIfNeeded(paintInfo, paintOffset);
 }
 
 static inline bool rendererObscuresBackground(RenderBox* rootBox)
 {
     ASSERT(rootBox);
-    RenderStyle* style = rootBox->style();
+    const RenderStyle* style = rootBox->style();
     if (style->visibility() != VISIBLE
         || style->opacity() != 1
         || style->hasFilter()
         || style->hasTransform())
         return false;
 
     if (rootBox->compositingState() == PaintsIntoOwnBacking)
         return false;
 
     const RenderObject* rootRenderer = rootBox->rendererForRootBackground();
@@ skipping 46 matching lines @@
 {
     ASSERT(rootBox);
     // CSS Boxes always fill the viewport background (see paintRootBoxFillLayers)
     if (!rootBox->isSVG())
         return true;
 
     return rootBox->frameRect().contains(m_renderView.frameRect());
 }
 
 } // namespace blink