Make RenderObject::style() return a const object

Source/core/rendering/compositing/CompositedLayerMapping.cpp

Index: Source/core/rendering/compositing/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/compositing/CompositedLayerMapping.cpp b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
index d2001a5dfb27969921c85b632ab4003729352b22..f400a2c100e9501875b4a83bc5de541052651130 100644
--- a/Source/core/rendering/compositing/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
@@ -448,7 +448,7 @@ bool CompositedLayerMapping::updateGraphicsLayerConfiguration()
         layerConfigChanged = true;
 
     bool hasPerspective = false;
-    if (RenderStyle* style = renderer->style())
+    if (const RenderStyle* style = renderer->style())
         hasPerspective = style->hasPerspective();
     bool needsChildTransformLayer = hasPerspective && (layerForChildrenTransform() == m_childTransformLayer.get()) && renderer->isBox();
     if (updateChildTransformLayer(needsChildTransformLayer))
@@ -1466,7 +1466,7 @@ void CompositedLayerMapping::updateShouldFlattenTransform()
     // so that the transform propagates to child layers correctly.
     if (GraphicsLayer* childTransformLayer = layerForChildrenTransform()) {
         bool hasPerspective = false;
-        if (RenderStyle* style = m_owningLayer.renderer()->style())
+        if (const RenderStyle* style = m_owningLayer.renderer()->style())
             hasPerspective = style->hasPerspective();
         if (hasPerspective)
             childTransformLayer->setShouldFlattenTransform(false);
@@ -1893,7 +1893,7 @@ void CompositedLayerMapping::updateImageContents()
 
 FloatPoint3D CompositedLayerMapping::computeTransformOrigin(const IntRect& borderBox) const
 {
-    RenderStyle* style = renderer()->style();
+    const RenderStyle* style = renderer()->style();
 
     FloatPoint3D origin;
     origin.setX(floatValueForLength(style->transformOriginX(), borderBox.width()));