修复 async 引入 mip 核心情况下的报错问题和性能打点问题

[zoumiaojiang]

相关 ISSUE: （ISSUE 链接地址）

513 #514

1、升级点 （清晰准确的描述升级的功能点）

• 修复 async 引入模式下 document.body 为 null 的情况
• 修复 performance 在 async 引入模式下的 DOMContentLoaded 事件响应问题

2、影响范围 （描述该需求上线会影响什么功能）

由于调整了 viewport 执行时机，可能会影响一些整体 viewport 效果

3、自测 Checklist

4、需要覆盖的场景和 Case

• [ ] 是否覆盖了 sf 打开 MIP 页
• [ ] 是否验证了极速服务 MIP 页面效果

5、自测机型和浏览器

• [ ] 是否覆盖了 iOS 系统手机
• [ ] 是否覆盖了 Android 系统手机
• [ ] 是否覆盖了 iPhone 版式浏览器（比如 QQ、UC、Chrome、Safari、安卓自带浏览器）
• [ ] 是否覆盖了手百

[coveralls]

Pull Request Test Coverage Report for Build 925

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 7 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 94.631%

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Files with Coverage Reduction	New Missed Lines	%
src/performance.js	7	83.75%
<!--	Total:	7		-->

Totals
Change from base Build 920:	0.04%
Covered Lines:	3662
Relevant Lines:	3792

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 917

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 20 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.2%) to 94.43%

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Files with Coverage Reduction	New Missed Lines	%
src/util/dom/rect.js	5	69.23%
src/performance.js	7	83.75%
src/util/dom/dom.js	8	86.0%
<!--	Total:	20		-->

Totals
Change from base Build 932:	-0.2%
Covered Lines:	3713
Relevant Lines:	3853

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💛 - Coveralls