Make RenderObject::style() return a const object

Source/core/layout/LayoutTheme.cpp

 /**
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, Inc.
  *
  * 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.
  *
@@ skipping 821 matching lines @@
     double max = input->maximum();
     ControlPart part = o->style()->appearance();
     // We don't support ticks on alternate sliders like MediaVolumeSliders.
     if (part !=  SliderHorizontalPart && part != SliderVerticalPart)
         return;
     bool isHorizontal = part ==  SliderHorizontalPart;
 
     IntSize thumbSize;
     RenderObject* thumbRenderer = input->userAgentShadowRoot()->getElementById(ShadowElementNames::sliderThumb())->renderer();
     if (thumbRenderer) {
-        RenderStyle* thumbStyle = thumbRenderer->style();
+        const RenderStyle* thumbStyle = thumbRenderer->style();
         int thumbWidth = thumbStyle->width().intValue();
         int thumbHeight = thumbStyle->height().intValue();
         thumbSize.setWidth(isHorizontal ? thumbWidth : thumbHeight);
         thumbSize.setHeight(isHorizontal ? thumbHeight : thumbWidth);
     }
 
     IntSize tickSize = sliderTickSize();
     float zoomFactor = o->style()->effectiveZoom();
     FloatRect tickRect;
     int tickRegionSideMargin = 0;
@@ skipping 279 matching lines @@
 bool LayoutTheme::supportsCalendarPicker(const AtomicString& type) const
 {
     return type == InputTypeNames::date
         || type == InputTypeNames::datetime
         || type == InputTypeNames::datetime_local
         || type == InputTypeNames::month
         || type == InputTypeNames::week;
 }
 #endif
 
-bool LayoutTheme::shouldUseFallbackTheme(RenderStyle*) const
+bool LayoutTheme::shouldUseFallbackTheme(const RenderStyle*) const
 {
     return false;
 }
 
 void LayoutTheme::adjustStyleUsingFallbackTheme(RenderStyle* style, Element* e)
 {
     ControlPart part = style->appearance();
     switch (part) {
     case CheckboxPart:
         return adjustCheckboxStyleUsingFallbackTheme(style, e);
@@ skipping 105 matching lines @@
 
     // padding - not honored by WinIE, needs to be removed.
     style->resetPadding();
 
     // border - honored by WinIE, but looks terrible (just paints in the control box and turns off the Windows XP theme)
     // for now, we will not honor it.
     style->resetBorder();
 }
 
 } // namespace blink