Make RenderObject::style() return a const object

Source/core/dom/TreeScope.cpp

Index: Source/core/dom/TreeScope.cpp
diff --git a/Source/core/dom/TreeScope.cpp b/Source/core/dom/TreeScope.cpp
index 235f220317df7067f2331f228c35a1b5a14c52b8..7e3410bd0dc2f54dcbce9b541e900ce5aaba2c28 100644
--- a/Source/core/dom/TreeScope.cpp
+++ b/Source/core/dom/TreeScope.cpp
@@ -507,7 +507,7 @@ void TreeScope::setNeedsStyleRecalcForViewportUnits()
     for (Element* element = ElementTraversal::firstWithin(rootNode()); element; element = ElementTraversal::nextIncludingPseudo(*element)) {
         for (ShadowRoot* root = element->youngestShadowRoot(); root; root = root->olderShadowRoot())
             root->setNeedsStyleRecalcForViewportUnits();
-        LayoutStyle* style = element->layoutStyle();
+        const LayoutStyle* style = element->layoutStyle();
         if (style && style->hasViewportUnits())
             element->setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::ViewportUnits));
     }