Switch SupportsUserData uses to use unique_ptr.

content/test/web_contents_observer_sanity_checker.h

Index: content/test/web_contents_observer_sanity_checker.h
diff --git a/content/test/web_contents_observer_sanity_checker.h b/content/test/web_contents_observer_sanity_checker.h
index 86fc9e9ec04a250ea9f928785827b7fa825fca46..f8f6a2ba6a86844d2e93e8ff60b53e6994309464 100644
--- a/content/test/web_contents_observer_sanity_checker.h
+++ b/content/test/web_contents_observer_sanity_checker.h
@@ -30,6 +30,8 @@ namespace content {
 class WebContentsObserverSanityChecker : public WebContentsObserver,
                                          public base::SupportsUserData::Data {
  public:
+  ~WebContentsObserverSanityChecker() override;
+
   // Enables these checks on |web_contents|. Usually ContentBrowserSanityChecker
   // should call this for you.
   static void Enable(WebContents* web_contents);
@@ -76,7 +78,6 @@ class WebContentsObserverSanityChecker : public WebContentsObserver,
 
  private:
   explicit WebContentsObserverSanityChecker(WebContents* web_contents);
-  ~WebContentsObserverSanityChecker() override;
 
   std::string Format(RenderFrameHost* render_frame_host);
   void AssertRenderFrameExists(RenderFrameHost* render_frame_host);