core(tracehouse): fixup parent tasks when fudging endTime (#16420)

Author: connorjclark

core/lib/tracehouse/main-thread-tasks.js

@@ -267,6 +267,14 @@ class MainThreadTasks {
             // It's less than 1ms, we'll let it slide by increasing the duration of the parent.
             currentTask.endTime = nextTask.endTime;
             currentTask.duration += timeDelta;
+
+            // Recursively extend parent endTimes, as needed.
+            let cur = currentTask.parent;
+            while (cur && cur.endTime < nextTask.endTime) {
+              cur.duration += nextTask.endTime - cur.endTime;
+              cur.endTime = nextTask.endTime;
+              cur = cur.parent;
+            }
           } else if (nextTask.unbounded) {
             // It's ending at traceEndTs, it means we were missing the end event. We'll truncate it to the parent.
             nextTask.endTime = currentTask.endTime;