WebUI: Fix crash while loading scripts for webview.[add/remove]ContentScripts API.

extensions/browser/user_script_loader.h

Index: extensions/browser/user_script_loader.h
diff --git a/extensions/browser/user_script_loader.h b/extensions/browser/user_script_loader.h
index a6a5d7c9ef23d0845026a8fa4cf6cf0f80ec6517..c09166296835a96ab5624577d257b88d5aa28d55 100644
--- a/extensions/browser/user_script_loader.h
+++ b/extensions/browser/user_script_loader.h
@@ -95,7 +95,8 @@ class UserScriptLoader : public content::NotificationObserver {
   void RemoveObserver(Observer* observer);
 
  protected:
-  // Allows the derived classes have different ways to load user scripts.
+  // Allows the derived classes to have different ways to load user scripts.
+  // This may not be synchronous with the calls to Add/Remove/Clear scripts.
   virtual void LoadScripts(std::unique_ptr<UserScriptList> user_scripts,
                            const std::set<HostID>& changed_hosts,
                            const std::set<int>& added_script_ids,