1. 构造函数
2. PaymentRequest
3. 属性
4. hashCode
5. id
6. on
7. runtimeType
8. shippingAddress
9. shippingOption
10. shippingType
11. 方法
12. abort
13. addEventListener
14. canMakePayment
15. dispatchEvent
16. noSuchMethod
17. removeEventListener
18. show
19. toString
20. 运算符
21. 运算符 ==