Add missing documentation

docs/api/browser-window.md

@@ -289,6 +289,7 @@ The `webPreferences` option is an object that can have the following properties:
   when the page becomes background. Defaults to `true`.
 * `offscreen` Boolean - Whether to enable offscreen rendering for the browser
   window. Defaults to `false`.
+* `sandbox` Boolean - Whether to enable Chromium OS-level sandbox.
 
 ### Instance Events
 

docs/api/tray.md

@@ -251,4 +251,8 @@ Returns `Object`:
 
 The `bounds` of this tray icon as `Object`.
 
+#### `tray.isDestroyed()`
+
+Returns `Boolean` - Whether the tray icon is destroyed.
+
 [event-emitter]: http://nodejs.org/api/events.html#events_class_events_eventemitter