phantomjs: performance.getEntriesByType not supported (#21009)

public/app/app.ts

@@ -175,7 +175,7 @@ export class GrafanaApp {
 
 
     ttiPolyfill.getFirstConsistentlyInteractive().then((tti: any) => {
     ttiPolyfill.getFirstConsistentlyInteractive().then((tti: any) => {
       // Collecting paint metrics first
       // Collecting paint metrics first
-      const paintMetrics = performance.getEntriesByType('paint');
+      const paintMetrics = performance && performance.getEntriesByType ? performance.getEntriesByType('paint') : [];
 
 
       for (const metric of paintMetrics) {
       for (const metric of paintMetrics) {
         reportPerformance(metric.name, Math.round(metric.startTime + metric.duration));
         reportPerformance(metric.name, Math.round(metric.startTime + metric.duration));