[Bug Report] When scroll appears vertically in tabs, the activated tab is out of visual range

[fangcw]

Element UI version

2.10.1

OS/Browsers version

macOS10.14.3/Chrome 75.0.3770.100

Vue version

2.6.10

Reproduction Link

https://codepen.io/fangcw/pen/mZZJYg

Steps to reproduce

1. tabs 纵向出现scroll
2. 设置默认激活的tab在可视范围外
3. 激活的tab并没有滚动至可视范围内

What is Expected?

tabs 纵向出现scroll时，默认激活的tab在可视范围内

What is actually happening?

tabs 纵向出现scroll时，默认激活的tab不在可视范围内

[element-bot]

Translation of this issue:

Element UI version

2.10.1

OS/Browsers version

MacOS 10.14.3/Chrome 75.0.3770.100

Vue version

2.6.10

Reproduction Link

Https://codepen.io/fangcw/pen/mZJYg

Steps to reproduce

1. scroll appears vertically in tabs

2. Set the default activated tab outside the visual range

3. Activated tabs do not scroll to the visible range

What is Expected?

When scroll appears vertically in tabs, the default activated tab is visible

What is actually happening?

When scroll appears vertically in tabs, the default activated tab is not visible