const runtime.traceEvNextGC

3 uses

	runtime (current package)
		trace.go#L57: 	traceEvNextGC            = 34 // memstats.next_gc change [timestamp, next_gc]
		trace.go#L1152: 		traceEvent(traceEvNextGC, -1, 0)
		trace.go#L1154: 		traceEvent(traceEvNextGC, -1, nextGC)