tti: simplify logic grabbing 85% vis complete

Author: paulirish

lighthouse-core/audits/time-to-interactive.js

@@ -79,21 +79,17 @@ class TTIMetric extends Audit {
       const fMPts = timings.fMPfull + timings.navStart;
 
       // look at speedline results for 85% starting at FMP
-      let eightyFivePctVC;
       let visuallyReadyTiming = 0;
 
       if (artifacts.Speedline.frames) {
-        eightyFivePctVC = artifacts.Speedline.frames.find(frame => {
+        const eightyFivePctVC = artifacts.Speedline.frames.find(frame => {
           return frame.getTimeStamp() >= fMPts && frame.getProgress() >= 85;
         });
 
-        // Check to avoid closure compiler null dereferencing errors
-        if (eightyFivePctVC === undefined) {
-          eightyFivePctVC = 0;
+        if (eightyFivePctVC) {
+          // TODO CHECK these units are the same
+          visuallyReadyTiming = eightyFivePctVC.getTimeStamp() - timings.navStart;
         }
-
-        // TODO CHECK these units are the same
-        visuallyReadyTiming = eightyFivePctVC.getTimeStamp() - timings.navStart || 0;
       }
 
       // Find first 500ms window where Est Input Latency is <50ms at the 90% percentile.