mac版dock栏的图标过大，不协调 #981

Bug report?

• Please describe the steps to reproduce as detailed as possible.

Feature request?

• Besides telling me what you want, please also describe what it does and why you need it.
• To avoid duplicates, please also check out the requested features before you post: Requested features | 已收集的建议 #282

发现了 bug？

• 请描述一下重现的步骤，越详细越好

请求新功能？

• 除了告诉我你想要什么，请再描述一下它具体是怎样的，以及你为什么需要它
• 为避免重复，发布之前请检查一下它是否已被提出过：Requested features | 已收集的建议 #282