Make RenderObject::style() return a const object

Source/core/layout/LayoutMedia.cpp

Index: Source/core/layout/LayoutMedia.cpp
diff --git a/Source/core/layout/LayoutMedia.cpp b/Source/core/layout/LayoutMedia.cpp
index 490f0f0d68ac4494a0c53fa2d6184eb4a31d889a..8917706d5c87902a705fff275326c1ce6456a3d5 100644
--- a/Source/core/layout/LayoutMedia.cpp
+++ b/Source/core/layout/LayoutMedia.cpp
@@ -65,8 +65,8 @@ void LayoutMedia::layout()
     LayoutState state(*this, locationOffset());
 
     controlsRenderer->setLocation(LayoutPoint(borderLeft(), borderTop()) + LayoutSize(paddingLeft(), paddingTop()));
-    controlsRenderer->style()->setHeight(Length(newSize.height(), Fixed));
-    controlsRenderer->style()->setWidth(Length(newSize.width(), Fixed));
+    controlsRenderer->mutableStyleRef().setHeight(Length(newSize.height(), Fixed));
+    controlsRenderer->mutableStyleRef().setWidth(Length(newSize.width(), Fixed));
     controlsRenderer->forceLayout();
     clearNeedsLayout();
 }