Switch SupportsUserData uses to use unique_ptr.

chrome/browser/task_manager/providers/web_contents/prerender_tag.h

Index: chrome/browser/task_manager/providers/web_contents/prerender_tag.h
diff --git a/chrome/browser/task_manager/providers/web_contents/prerender_tag.h b/chrome/browser/task_manager/providers/web_contents/prerender_tag.h
index d637eff5ba2c4be35ca665a52046d184eeaed98a..d4c3e5204429977ca1fda888551c8b0814b38e34 100644
--- a/chrome/browser/task_manager/providers/web_contents/prerender_tag.h
+++ b/chrome/browser/task_manager/providers/web_contents/prerender_tag.h
@@ -15,6 +15,8 @@ namespace task_manager {
 // PrerenderManager.
 class PrerenderTag : public WebContentsTag {
  public:
+  ~PrerenderTag() override;
+
   // task_manager::WebContentsTag:
   PrerenderTask* CreateTask() const override;
 
@@ -22,7 +24,6 @@ class PrerenderTag : public WebContentsTag {
   friend class WebContentsTags;
 
   explicit PrerenderTag(content::WebContents* web_contents);
-  ~PrerenderTag() override;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderTag);
 };