Remove implicit conversions from scoped_refptr to T* in FileWatcher.

base/files/file_path_watcher.h

Index: base/files/file_path_watcher.h
diff --git a/base/files/file_path_watcher.h b/base/files/file_path_watcher.h
index b90efa1800fb7eeaa2cfc2d268dc1c09dfd89c4b..d26fa060446cad94cf5c04d027eacac3931489fe 100644
--- a/base/files/file_path_watcher.h
+++ b/base/files/file_path_watcher.h
@@ -62,7 +62,7 @@ class BASE_EXPORT FilePathWatcher {
       return message_loop_;
     }
 
-    void set_message_loop(base::MessageLoopProxy* loop) {
+    void set_message_loop(const scoped_refptr<base::MessageLoopProxy>& loop) {
       message_loop_ = loop;
     }