1. 构造函数
2. MediaStreamEvent
3. 属性
4. bubbles
5. cancelable
6. composed
7. currentTarget
8. defaultPrevented
9. eventPhase
10. hashCode
11. isTrusted
12. matchingTarget
13. path
14. runtimeType
15. stream
16. target
17. timeStamp
18. type
19. 方法
20. composedPath
21. noSuchMethod
22. preventDefault
23. stopImmediatePropagation
24. stopPropagation
25. toString
26. 操作符
27. 操作符 ==
28. 静态属性
29. supported