Make RenderObject::style() return a const object

Source/core/paint/TextPainter.h

 // 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.
 
 #ifndef TextPainter_h
 #define TextPainter_h
 
 #include "core/rendering/FloatToLayoutUnit.h"
 #include "core/rendering/style/RenderStyleConstants.h"
 #include "platform/fonts/TextBlob.h"
@@ skipping 39 matching lines @@
         bool operator==(const Style& other)
         {
             return fillColor == other.fillColor
                 && strokeColor == other.strokeColor
                 && emphasisMarkColor == other.emphasisMarkColor
                 && strokeWidth == other.strokeWidth
                 && shadow == other.shadow;
         }
         bool operator!=(const Style& other) { return !(*this == other); }
     };
-    static Style textPaintingStyle(RenderObject&, RenderStyle*, bool forceBlackText, bool isPrinting);
+    static Style textPaintingStyle(RenderObject&, const RenderStyle*, bool forceBlackText, bool isPrinting);
     static Style selectionPaintingStyle(RenderObject&, bool haveSelection, bool forceBlackText, bool isPrinting, const Style& textStyle);
 
     enum RotationDirection { Counterclockwise, Clockwise };
     static AffineTransform rotation(const FloatRectWillBeLayoutRect& boxRect, RotationDirection);
 
 private:
     void updateGraphicsContext(const Style& style, GraphicsContextStateSaver& saver)
     {
         updateGraphicsContext(m_graphicsContext, style, m_horizontal, saver);
     }
@@ skipping 21 matching lines @@
 
 inline AffineTransform TextPainter::rotation(const FloatRectWillBeLayoutRect& boxRect, RotationDirection rotationDirection)
 {
     return rotationDirection == Clockwise ? AffineTransform(0, 1, -1, 0, boxRect.x() + boxRect.maxY(), boxRect.maxY() - boxRect.x())
         : AffineTransform(0, -1, 1, 0, boxRect.x() - boxRect.maxY(), boxRect.x() + boxRect.maxY());
 }
 
 } // namespace blink
 
 #endif // TextPainter_h