Remove seemingly unused method declaration on Element.h

Review-Url: https://codereview.chromium.org/2280833002
Cr-Commit-Position: refs/heads/master@{#414669}

third_party/WebKit/Source/core/dom/Element.h

@@ -663,7 +663,6 @@ private:
     void updatePresentationAttributeStyle();
 
     void inlineStyleChanged();
-    PropertySetCSSStyleDeclaration* inlineStyleCSSOMWrapper();
     void setInlineStyleFromString(const AtomicString&);
 
     // If the only inherited changes in the parent element are independent,