webview: add permission-request event

atom/browser/api/atom_api_web_contents.h

@@ -195,6 +195,10 @@ class WebContents : public mate::TrackableObject<WebContents>,
                  const gfx::Rect& selection_rect,
                  int active_match_ordinal,
                  bool final_update) override;
+  void RequestMediaAccessPermission(
+      content::WebContents* web_contents,
+      const content::MediaStreamRequest& request,
+      const content::MediaResponseCallback& callback) override;
 
   // content::WebContentsObserver:
   void BeforeUnloadFired(const base::TimeTicks& proceed_time) override;