Make RenderObject::style() return a const object

Source/core/dom/NodeRenderStyle.h

Index: Source/core/dom/NodeRenderStyle.h
diff --git a/Source/core/dom/NodeRenderStyle.h b/Source/core/dom/NodeRenderStyle.h
index 5a38d3a1b810438000f3e81529da1a2b20510afd..35317250a84e6dde67082b39c67f357694394fcf 100644
--- a/Source/core/dom/NodeRenderStyle.h
+++ b/Source/core/dom/NodeRenderStyle.h
@@ -33,10 +33,10 @@
 
 namespace blink {
 
-inline RenderStyle* Node::renderStyle() const
+inline RenderStyle* Node::mutableRenderStyle() const
 {
     if (RenderObject* renderer = this->renderer())
-        return renderer->style();
+        return renderer->deprecatedMutableStyle();
     // <option> and <optgroup> can be styled even if they don't get renderers,
     // so they store their style internally and return it through nonRendererStyle().
     // We check here explicitly to avoid the virtual call in the common case.
@@ -45,7 +45,12 @@ inline RenderStyle* Node::renderStyle() const
     return 0;
 }
 
-inline RenderStyle* Node::parentRenderStyle() const
+inline const RenderStyle* Node::renderStyle() const
+{
+    return mutableRenderStyle();
+}
+
+inline const RenderStyle* Node::parentRenderStyle() const
 {
     ContainerNode* parent = NodeRenderingTraversal::parent(*this);
     return parent ? parent->renderStyle() : 0;