metamask-extension/app/scripts/lib/ipfsContent.js

const extension = require('extensionizer')
const resolver = require('./resolver.js')

module.exports = function (provider) {
    function ipfsContent (details) {
      const name = details.url.substring(7, details.url.length - 1)
      let clearTime = null
      extension.tabs.getSelected(null, tab => {
          extension.tabs.update(tab.id, { url: 'loading.html' })

          clearTime = setTimeout(() => {
              return extension.tabs.update(tab.id, { url: '404.html' })
          }, 60000)

          resolver.resolve(name, provider).then(ipfsHash => {
              clearTimeout(clearTime)
              let url = 'https://ipfs.infura.io/ipfs/' + ipfsHash
              return fetch(url, { method: 'HEAD' }).then(response => response.status).then(statusCode => {
                  if (statusCode !== 200) return extension.tabs.update(tab.id, { url: '404.html' })
                  extension.tabs.update(tab.id, { url: url })
              })
              .catch(err => {
                  url = 'https://ipfs.infura.io/ipfs/' + ipfsHash
                  extension.tabs.update(tab.id, {url: url})
                  return err
              })
          })
          .catch(err => {
              clearTimeout(clearTime)
              const url = err === 'unsupport' ? 'unsupport' : 'error'
              extension.tabs.update(tab.id, {url: `${url}.html?name=${name}`})
          })
      })
      return { cancel: true }
    }

    extension.webRequest.onBeforeRequest.addListener(ipfsContent, {urls: ['*://*.eth/', '*://*.test/']})

    return {
      remove () {
        extension.webRequest.onBeforeRequest.removeListener(ipfsContent)
      },
    }
}