Avoid process reference error (#739)
Avoid process reference error (#739)

Seems the typo in code. Similar issue hwas fixed here: #726

Exception output:

```
Uncaught (in promise) ReferenceError: process is not defined
    at warning (react-utils.js:75)
    at warnOnce (react-utils.js:92)
    at checkIfStyleSheetIsImported (react-utils.js:132)
    at XYPlot.componentDidMount (xy-plot.js:165)
    at eval (ReactCompositeComponent.js:262)
    at measureLifeCyclePerf (ReactCompositeComponent.js:73)
    at eval (ReactCompositeComponent.js:261)
    at CallbackQueue.notifyAll (CallbackQueue.js:74)
    at ReactReconcileTransaction.close (ReactReconcileTransaction.js:78)
    at ReactReconcileTransaction.closeAll (Transaction.js:207)
```
uber-common/react-vis,uber/react-vis,uber/react-vis,uber-common/react-vis,uber/react-vis