Make RenderObject::style() return a const object

Source/core/css/resolver/StyleResolverState.cpp

Index: Source/core/css/resolver/StyleResolverState.cpp
diff --git a/Source/core/css/resolver/StyleResolverState.cpp b/Source/core/css/resolver/StyleResolverState.cpp
index 91db70a47e366b898cef2ee5a5b8126cf5b120cb..257cf2724ecc9cb80a6fc0f234b284bed9ed534e 100644
--- a/Source/core/css/resolver/StyleResolverState.cpp
+++ b/Source/core/css/resolver/StyleResolverState.cpp
@@ -29,7 +29,7 @@
 
 namespace blink {
 
-StyleResolverState::StyleResolverState(Document& document, const ElementResolveContext& elementContext, RenderStyle* parentStyle)
+StyleResolverState::StyleResolverState(Document& document, const ElementResolveContext& elementContext, const RenderStyle* parentStyle)
     : m_elementContext(elementContext)
     , m_document(document)
     , m_style(nullptr)
@@ -45,7 +45,7 @@ StyleResolverState::StyleResolverState(Document& document, const ElementResolveC
     m_elementStyleResources.setDeviceScaleFactor(document.frameHost()->deviceScaleFactor());
 }
 
-StyleResolverState::StyleResolverState(Document& document, Element* element, RenderStyle* parentStyle)
+StyleResolverState::StyleResolverState(Document& document, Element* element, const RenderStyle* parentStyle)
     : StyleResolverState(document, element ? ElementResolveContext(*element) : ElementResolveContext(document), parentStyle)
 {
 }