[Extensions] Add more bindings access checks

BUG=598165

Review URL: https://codereview.chromium.org/1854983002

Cr-Commit-Position: refs/heads/master@{#385282}
 NotificationsNativeHandler::NotificationsNativeHandler(ScriptContext* context)
     : ObjectBackedNativeHandler(context) {
   RouteFunction(
      "GetNotificationImageSizes", "notifications",
       base::Bind(&NotificationsNativeHandler::GetNotificationImageSizes,
                  base::Unretained(this)));
 }

 NotificationsNativeHandler::NotificationsNativeHandler(ScriptContext* context)
     : ObjectBackedNativeHandler(context) {
   RouteFunction(
      "GetNotificationImageSizes",
       base::Bind(&NotificationsNativeHandler::GetNotificationImageSizes,
                  base::Unretained(this)));
 }
