[core] fix containing block size of absolutely positioned element

[Fitzmaz]

Fix http://dotwe.org/vue/8d92197521649a17842fddf7cf67cc76

Brief Description of the PR

According to this reference:

If the position property is absolute, the containing block is formed by the edge of the padding box of the nearest ancestor element that has a position value other than static (fixed, absolute, relative, or sticky).

The border of the ancestor element should be excluded when calculating the size of the containing block.

Checklist

• Demo:
  http://dotwe.org/vue/8d92197521649a17842fddf7cf67cc76
• Documentation:

[CLAassistant]

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