internal/trace: change Less to make sorting events deterministice

    The existing code just used timestamps. The new code uses more fields
    when timestamps are equal.

	Revised to shorten code per reviewer comments.

Change-Id: Ibd0824d0acd7644484d536b1a754a0da156fac3d
Reviewed-on: https://go-review.googlesource.com/113721Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

src/internal/trace/order.go

@@ -133,7 +133,7 @@ func order1007(m map[int][]*Event) (events []*Event, err error) {
 			ev.Ts = ts
 		}
 	}
-	sort.Stable(eventList(events))
+	sort.Sort(eventList(events))
 
 	return
 }
@@ -243,7 +243,20 @@ func (l orderEventList) Len() int {
 }
 
 func (l orderEventList) Less(i, j int) bool {
-	return l[i].ev.Ts < l[j].ev.Ts
+	a, b := l[i].ev, l[j].ev
+	if a.Ts != b.Ts {
+		return a.Ts < b.Ts
+	}
+	if a.Type != b.Type {
+		return a.Type < b.Type
+	}
+	if a.P != b.P {
+		return a.P < b.P
+	}
+	if a.G != b.G {
+		return a.G < b.G
+	}
+	return a.Args[0] < b.Args[0]
 }
 
 func (l orderEventList) Swap(i, j int) {