old_contents: import Document, { Head, Main, NextScript } from 'next/document'
  import React from 'react'
  import { AppRegistry } from 'react-native-web'
  import config from '../app.json'
  // Force Next-generated DOM elements to fill their parent's height
  const normalizeNextElements = `
    #__next {
      display: flex;
      flex-direction: column;
      height: 100%;
    }
  `
  
  export default class MyDocument extends Document {
    static async getInitialProps ({ renderPage }) {
      AppRegistry.registerComponent(config.name, () => Main)
      const { getStyleElement } = AppRegistry.getApplication(config.name)
      const page = renderPage()
      const styles = [
        <style dangerouslySetInnerHTML={{ __html: normalizeNextElements }} />,
        getStyleElement()
      ]
      return { ...page, styles: React.Children.toArray(styles) }
    }
  
    render () {
      return (
        <html style={{ height: '100%' }}>
          <Head>
            <meta name='viewport' content='width=device-width, initial-scale=1' />
          </Head>
          <body style={{ height: '100%', overflow: 'hidden' }}>
            <Main />
            <NextScript />
          </body>
        </html>
      )
    }
  }
  
new_contents: import Document, { Head, Main, NextScript } from 'next/document'
  import React from 'react'
  import { AppRegistry } from 'react-native'
  import config from '../app.json'
  // Force Next-generated DOM elements to fill their parent's height
  const normalizeNextElements = `
    #__next {
      display: flex;
      flex-direction: column;
      height: 100%;
    }
  `
  
  export default class MyDocument extends Document {
    static async getInitialProps ({ renderPage }) {
      AppRegistry.registerComponent(config.name, () => Main)
      const { getStyleElement } = AppRegistry.getApplication(config.name)
      const page = renderPage()
      const styles = [
        <style dangerouslySetInnerHTML={{ __html: normalizeNextElements }} />,
        getStyleElement()
      ]
      return { ...page, styles: React.Children.toArray(styles) }
    }
  
    render () {
      return (
        <html style={{ height: '100%' }}>
          <Head>
            <meta name='viewport' content='width=device-width, initial-scale=1' />
          </Head>
          <body style={{ height: '100%', overflow: 'hidden' }}>
            <Main />
            <NextScript />
          </body>
        </html>
      )
    }
  }
  
subject: Fix react-native-web example FOUC (#8576)