core/dev-utils/hotDevClient.js
function handleSuccess() {
  clearOutdatedErrors()

  var isHotUpdate = !isFirstCompilation
  isFirstCompilation = false
  hasCompileErrors = false

  // Attempt to apply hot updates or reload.
  if (isHotUpdate) {
    tryApplyUpdates(function onHotUpdateSuccess() {
      // Only dismiss it when we're sure it's a hot update.
      // Otherwise it would flicker right before the reload.
      ErrorOverlay.dismissBuildError()
    })
  }
}
function handleSuccess() {
  clearOutdatedErrors()

  var isHotUpdate = !isFirstCompilation
  isFirstCompilation = false
  hasCompileErrors = false

  // Attempt to apply hot updates or reload.
  if (isHotUpdate) {
    tryApplyUpdates(function onHotUpdateSuccess() {
      // Only dismiss it when we're sure it's a hot update.
      // Otherwise it would flicker right before the reload.
      ErrorOverlay.dismissBuildError()
    })
  }
}
Successful compilation.