Fix some WeakPtrFactory members that aren't last

ppapi/shared_impl/resource_tracker.h

Index: ppapi/shared_impl/resource_tracker.h
diff --git a/ppapi/shared_impl/resource_tracker.h b/ppapi/shared_impl/resource_tracker.h
index ee93376b4ca5b8931ea60fb0baaf2b5986af0250..6feeea7692bd800c9189a4579b333797550d03ce 100644
--- a/ppapi/shared_impl/resource_tracker.h
+++ b/ppapi/shared_impl/resource_tracker.h
@@ -126,14 +126,14 @@ class PPAPI_SHARED_EXPORT ResourceTracker {
 
   int32 last_resource_value_;
 
-  base::WeakPtrFactory<ResourceTracker> weak_ptr_factory_;
-
   // On the host side, we want to check that we are only called on the main
   // thread. This is to protect us from accidentally using the tracker from
   // other threads (especially the IO thread). On the plugin side, the tracker
   // is protected by the proxy lock and is thread-safe, so this will be NULL.
   scoped_ptr<base::ThreadChecker> thread_checker_;
 
+  base::WeakPtrFactory<ResourceTracker> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ResourceTracker);
 };