Implement PermissionService::GetNextPermissionChange.

content/public/browser/permission_manager.h

Index: content/public/browser/permission_manager.h
diff --git a/content/public/browser/permission_manager.h b/content/public/browser/permission_manager.h
index e7300751d00b1479d3a9a0c8a7622cbb0fc229f7..6a56e0b6a58b7be2cf05246d4e8371e7d766711b 100644
--- a/content/public/browser/permission_manager.h
+++ b/content/public/browser/permission_manager.h
@@ -43,6 +43,17 @@ class CONTENT_EXPORT PermissionManager {
   virtual void RegisterPermissionUsage(PermissionType permission,
                                        const GURL& requesting_origin,
                                        const GURL& embedding_origin) = 0;
+
+  // Runs the given |callback| whenever the |permission| associated with the
+  // pair { requesting_origin, embedding_origin } changes.
+  // Returns the subscription_id to be used to unsubscribe.
+  virtual int SubscribePermissionStatusChange(
+      PermissionType permission,
+      const GURL& requesting_origin,
+      const GURL& embedding_origin,
+      const base::Callback<void(PermissionStatus)>& callback) = 0;
+
+  virtual void UnsubscribePermissionStatusChange(int subscription_id) = 0;
 };
 
 }  // namespace content