Make RenderObject::style() return a const object

Source/core/paint/LayerPainter.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/LayerPainter.h"
 
 #include "core/frame/Settings.h"
 #include "core/page/Page.h"
 #include "core/paint/CompositingRecorder.h"
@@ skipping 88 matching lines @@
     localPaintFlags |= PaintLayerPaintingCompositingAllPhases;
     paintLayerContents(context, paintingInfo, localPaintFlags);
 }
 
 class ClipPathHelper {
 public:
     ClipPathHelper(GraphicsContext* context, const RenderLayer& renderLayer, const LayerPaintingInfo& paintingInfo, LayoutRect& rootRelativeBounds, bool& rootRelativeBoundsComputed,
         const LayoutPoint& offsetFromRoot, PaintLayerFlags paintFlags)
         : m_resourceClipper(0), m_clipStateSaver(*context, false), m_renderLayer(renderLayer), m_context(context)
     {
-        RenderStyle* style = renderLayer.renderer()->style();
+        const RenderStyle* style = renderLayer.renderer()->style();
 
         // Clip-path, like border radius, must not be applied to the contents of a composited-scrolling container.
         // It must, however, still be applied to the mask layer, so that the compositor can properly mask the
         // scrolling contents and scrollbars.
         if (!renderLayer.renderer()->hasClipPath() || !style || (renderLayer.needsCompositedScrolling() && !(paintFlags & PaintLayerPaintingChildClippingMaskPhase)))
             return;
 
         m_clipperState = RenderSVGResourceClipper::ClipperNotApplied;
 
         ASSERT(style->clipPath());
@@ skipping 603 matching lines @@
     if (!m_renderLayer.containsDirtyOverlayScrollbars())
         return;
 
     LayerPaintingInfo paintingInfo(&m_renderLayer, enclosingIntRect(damageRect), paintBehavior, LayoutSize(), paintingRoot);
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_renderLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink