Use performance.mark() and performance.measure() in development

[Joe Lencioni]

It would be nice to have more insight into how react-with-styles is performing in real world applications. We can use performance.mark() and performance.measure() to annotate the user timing pane in Chrome's performance devtool.

[Jordan Harband]

We could maybe surround them in an env var so they get compiled out by default? We'll also have to make sure to always surround them in if (typeof performance !== 'undefined') since this code tends to run on the server too.

[Joe Lencioni]

Yes, absolutely. This should be contained in conditionals like:

if (process.env.NODE_ENV !== 'production') {
  ...
}