Explain why we don't use randomBytes on a comment

src/main-process/atom-application.js

@@ -92,6 +92,9 @@ const encryptOptions = (options, secret) => {

  // Even if the following IV is not cryptographically secure, there's a really good chance
  // it's going to be unique between executions which is the requirement for GCM.
  // We're not using `crypto.randomBytes()` because in electron v2, that API is really slow
  // on Windows machines, which affects the startup time of Atom.
  // TodoElectronIssue: Once we upgrade to electron v3 we can use `crypto.randomBytes()`
  const initVectorHash = crypto.createHash('sha1')
  initVectorHash.update(Date.now() + '')
  initVectorHash.update(Math.random() + '')