ensurePerformanceTimelineOrder = function() {
            if (!performanceTimelineRequiresSort) {
                return;
            }

            //
            // Measures, which may be in this list, may enter the list in
            // an unsorted order. For example:
            //
            //  1. measure("a")
            //  2. mark("start_mark")
            //  3. measure("b", "start_mark")
            //  4. measure("c")
            //  5. getEntries()
            //
            // When calling #5, we should return [a,c,b] because technically the start time
            // of c is "0" (navigationStart), which will occur before b's start time due to the mark.
            //
            performanceTimeline.sort(function(a, b) {
                return a.startTime - b.startTime;
            });

            performanceTimelineRequiresSort = false;
        }
Ensures our PT array is in the correct sorted order (by startTime)