Revert 190605 "Make RenderObject::style() return a const object"

trunk/Source/core/layout/LayoutSliderThumb.cpp

Index: trunk/Source/core/layout/LayoutSliderThumb.cpp
===================================================================
--- trunk/Source/core/layout/LayoutSliderThumb.cpp	(revision 190671)
+++ trunk/Source/core/layout/LayoutSliderThumb.cpp	(working copy)
@@ -45,15 +45,15 @@
 void LayoutSliderThumb::updateAppearance(const LayoutStyle& parentStyle)
 {
     if (parentStyle.appearance() == SliderVerticalPart)
-        mutableStyleRef().setAppearance(SliderThumbVerticalPart);
+        style()->setAppearance(SliderThumbVerticalPart);
     else if (parentStyle.appearance() == SliderHorizontalPart)
-        mutableStyleRef().setAppearance(SliderThumbHorizontalPart);
+        style()->setAppearance(SliderThumbHorizontalPart);
     else if (parentStyle.appearance() == MediaSliderPart)
-        mutableStyleRef().setAppearance(MediaSliderThumbPart);
+        style()->setAppearance(MediaSliderThumbPart);
     else if (parentStyle.appearance() == MediaVolumeSliderPart)
-        mutableStyleRef().setAppearance(MediaVolumeSliderThumbPart);
+        style()->setAppearance(MediaVolumeSliderThumbPart);
     else if (parentStyle.appearance() == MediaFullScreenVolumeSliderPart)
-        mutableStyleRef().setAppearance(MediaFullScreenVolumeSliderThumbPart);
+        style()->setAppearance(MediaFullScreenVolumeSliderThumbPart);
     if (style()->hasAppearance())
         LayoutTheme::theme().adjustSliderThumbSize(mutableStyleRef(), toElement(node()));
 }