PrerenderManager: No longer expose weak pointers.

chrome/browser/prerender/prerender_manager.h

Index: chrome/browser/prerender/prerender_manager.h
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index 83bd516b64b73a12326a400123cb58f121c3de61..6812e54204e0a1c47c4c192aba8f9983a9400db5 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -71,8 +71,7 @@ class PrerenderLocalPredictor;
 // PrerenderManager is responsible for initiating and keeping prerendered
 // views of web pages. All methods must be called on the UI thread unless
 // indicated otherwise.
-class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
-                         public content::NotificationObserver,
+class PrerenderManager : public content::NotificationObserver,
                          public content::RenderProcessHostObserver,
                          public KeyedService,
                          public MediaCaptureDevicesDispatcher::Observer {
@@ -588,6 +587,8 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   using PrerenderProcessSet = std::set<content::RenderProcessHost*>;
   PrerenderProcessSet prerender_process_hosts_;
 
+  base::WeakPtrFactory<PrerenderManager> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };