Get rid of unused declaration of Element::RecalcOwnStyleForReattach()

This patch gets rid of unused declaration |Element::RecalcOwnStyleForReattach()|
for improving code health.

Change-Id: I9c9b1331a59614d8bdf8f1ced03e4e8348db0da0
Reviewed-on: https://chromium-review.googlesource.com/1058877
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558644}

third_party/blink/renderer/core/dom/element.h

@@ -966,7 +966,6 @@ class CORE_EXPORT Element : public ContainerNode {
   scoped_refptr<ComputedStyle> PropagateInheritedProperties(StyleRecalcChange);
 
   StyleRecalcChange RecalcOwnStyle(StyleRecalcChange);
-  void RecalcOwnStyleForReattach();
   void RecalcShadowIncludingDescendantStylesForReattach();
   void RecalcShadowRootStylesForReattach();