Make RenderObject::style() return a const object

Source/core/css/SelectorChecker.cpp

Index: Source/core/css/SelectorChecker.cpp
diff --git a/Source/core/css/SelectorChecker.cpp b/Source/core/css/SelectorChecker.cpp
index 410cea96028b933a79131d0c0dc204ad93a89cdd..3de60a812ccc84cf4e9bc0c981a32a3cd5226f26 100644
--- a/Source/core/css/SelectorChecker.cpp
+++ b/Source/core/css/SelectorChecker.cpp
@@ -613,8 +613,8 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context, c
                 element.setStyleAffectedByEmpty();
                 if (context.elementStyle)
                     context.elementStyle->setEmptyState(result);
-                else if (element.renderStyle() && (element.document().styleEngine()->usesSiblingRules() || element.renderStyle()->unique()))
-                    element.renderStyle()->setEmptyState(result);
+                else if (element.mutableRenderStyle() && (element.document().styleEngine()->usesSiblingRules() || element.mutableRenderStyle()->unique()))
+                    element.mutableRenderStyle()->setEmptyState(result);
             }
             return result;
         }
@@ -690,7 +690,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context, c
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             int count = 1 + siblingTraversalStrategy.countElementsBefore(element);
             if (m_mode == ResolvingStyle) {
-                RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element.renderStyle();
+                RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element.mutableRenderStyle();
                 if (childStyle)
                     childStyle->setUnique();
                 parent->setChildrenAffectedByForwardPositionalRules();