class PageNavigator {
public:
// Opens a URL with the given disposition. The transition specifies how this
// navigation should be recorded in the history system (for example, typed).
virtual void OpenURL(const GURL& url, const GURL& referrer,
WindowOpenDisposition disposition,
PageTransition::Type transition) = 0;
};
我不明白那是什么=0; 部分......我们试图传达什么?