Make RenderObject::style() return a const object

Source/core/layout/LayoutSliderContainer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 82 matching lines @@
     // FIXME: The trackHeight should have been added before updateLogicalHeight was called to avoid this hack.
     setIntrinsicContentLogicalHeight(logicalHeight);
 
     RenderBox::computeLogicalHeight(logicalHeight, logicalTop, computedValues);
 }
 
 void LayoutSliderContainer::layout()
 {
     HTMLInputElement* input = toHTMLInputElement(node()->shadowHost());
     bool isVertical = hasVerticalAppearance(input);
-    style()->setFlexDirection(isVertical ? FlowColumn : FlowRow);
+    mutableStyleRef().setFlexDirection(isVertical ? FlowColumn : FlowRow);
     TextDirection oldTextDirection = style()->direction();
     if (isVertical) {
         // FIXME: Work around rounding issues in RTL vertical sliders. We want them to
         // render identically to LTR vertical sliders. We can remove this work around when
         // subpixel rendering is enabled on all ports.
-        style()->setDirection(LTR);
+        mutableStyleRef().setDirection(LTR);
     }
 
     Element* thumbElement = input->userAgentShadowRoot()->getElementById(ShadowElementNames::sliderThumb());
     Element* trackElement = input->userAgentShadowRoot()->getElementById(ShadowElementNames::sliderTrack());
     RenderBox* thumb = thumbElement ? thumbElement->renderBox() : 0;
     RenderBox* track = trackElement ? trackElement->renderBox() : 0;
 
     SubtreeLayoutScope layoutScope(*this);
     // Force a layout to reset the position of the thumb so the code below doesn't move the thumb to the wrong place.
     // FIXME: Make a custom Render class for the track and move the thumb positioning code there.
     if (track)
         layoutScope.setChildNeedsLayout(track);
 
     RenderFlexibleBox::layout();
 
-    style()->setDirection(oldTextDirection);
+    mutableStyleRef().setDirection(oldTextDirection);
     // These should always exist, unless someone mutates the shadow DOM (e.g., in the inspector).
     if (!thumb || !track)
         return;
 
     double percentageOffset = sliderPosition(input).toDouble();
     LayoutUnit availableExtent = isVertical ? track->contentHeight() : track->contentWidth();
     availableExtent -= isVertical ? thumb->size().height() : thumb->size().width();
     LayoutUnit offset = percentageOffset * availableExtent;
     LayoutPoint thumbLocation = thumb->location();
     if (isVertical)
         thumbLocation.setY(thumbLocation.y() + track->contentHeight() - thumb->size().height() - offset);
     else if (style()->isLeftToRightDirection())
         thumbLocation.setX(thumbLocation.x() + offset);
     else
         thumbLocation.setX(thumbLocation.x() - offset);
     thumb->setLocation(thumbLocation);
 
     // We need one-off invalidation code here because painting of the timeline element does not go through style.
     // Instead it has a custom implementation in C++ code.
     // Therefore the style system cannot understand when it needs to be paint invalidated.
     setShouldDoFullPaintInvalidation();
 }
 
 } // namespace blink