Update SupportsUserData uses with unique_ptr.

chrome/browser/supervised_user/supervised_user_interstitial.cc

Index: chrome/browser/supervised_user/supervised_user_interstitial.cc
diff --git a/chrome/browser/supervised_user/supervised_user_interstitial.cc b/chrome/browser/supervised_user/supervised_user_interstitial.cc
index 311e72546b36fd2b578dec67581a86bf6b23b61e..c4d5b28cdc36387dfbb7546770e3ab3c184f4792 100644
--- a/chrome/browser/supervised_user/supervised_user_interstitial.cc
+++ b/chrome/browser/supervised_user/supervised_user_interstitial.cc
@@ -53,6 +53,8 @@ namespace {
 
 class TabCloser : public content::WebContentsUserData<TabCloser> {
  public:
+  ~TabCloser() override {}
+
   static void MaybeClose(WebContents* web_contents) {
     DCHECK(web_contents);
 
@@ -75,7 +77,6 @@ class TabCloser : public content::WebContentsUserData<TabCloser> {
         FROM_HERE,
         base::Bind(&TabCloser::CloseTabImpl, weak_ptr_factory_.GetWeakPtr()));
   }
-  ~TabCloser() override {}
 
   void CloseTabImpl() {
     // On Android, FindBrowserWithWebContents and TabStripModel don't exist.