z-index changes after build(3.0)

[yuu2lee4]

Version

3.0.0-beta.2

Steps to reproduce

just build

What is expected?

z-index not changed

What is actually happening?

z-index changed

---

It is liked OptimizeCssPlugin's cssProcessor rebase z-index.It should set safe to true:

var OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')

.........
.........

// Compress extracted CSS. We are using this plugin so that possible
// duplicated CSS from different components can be deduped.
new OptimizeCSSPlugin({
 cssProcessorOptions: {
   safe: true
 }
})