Switch SupportsUserData uses to use unique_ptr.

ios/chrome/browser/web/network_activity_indicator_tab_helper.h

Index: ios/chrome/browser/web/network_activity_indicator_tab_helper.h
diff --git a/ios/chrome/browser/web/network_activity_indicator_tab_helper.h b/ios/chrome/browser/web/network_activity_indicator_tab_helper.h
index c264381bebdb393d68ca52e582fdc0e594c1e46f..083d8e69033c9cd2d36f1c5deecfe997befc8e5b 100644
--- a/ios/chrome/browser/web/network_activity_indicator_tab_helper.h
+++ b/ios/chrome/browser/web/network_activity_indicator_tab_helper.h
@@ -20,11 +20,12 @@ class NetworkActivityIndicatorTabHelper
     : public web::WebStateObserver,
       public web::WebStateUserData<NetworkActivityIndicatorTabHelper> {
  public:
+  ~NetworkActivityIndicatorTabHelper() override;
+
   static void CreateForWebState(web::WebState* web_state, NSString* tab_id);
 
  private:
   NetworkActivityIndicatorTabHelper(web::WebState* web_state, NSString* tab_id);
-  ~NetworkActivityIndicatorTabHelper() override;
 
   // web::WebStateObserver overrides:
   void DidStartLoading() override;