move history api feature detection to utils

js/controllers/location.js

@@ -1,3 +1,5 @@
+import { supportsHistoryAPI } from '../utils/device.js'
+
 /**
  * Reads and writes the URL based on reveal.js' current state.
  */
@@ -98,7 +100,7 @@ export default class Location {
 		else if( currentSlide ) {
 			// If we're configured to push to history OR the history
 			// API is not avaialble.
-			if( config.history || !window.history ) {
+			if( config.history || supportsHistoryAPI === false ) {
 				window.location.hash = this.getHash();
 			}
 			// If we're configured to reflect the current slide in the

js/utils/device.js

@@ -12,4 +12,6 @@ export const isAndroid = /android/gi.test( UA );
 // up slides. Zoom produces crisper results but has a lot of
 // xbrowser quirks so we only use it in whitelisted browsers.
 export const supportsZoom = 'zoom' in testElement.style && !isMobile &&
-				( isChrome || /Version\/[\d\.]+.*Safari/.test( UA ) );
+				( isChrome || /Version\/[\d\.]+.*Safari/.test( UA ) );
+
+export const supportsHistoryAPI = typeof window.history.replaceState === 'function' && !/PhantomJS/.test( UA );