cmd/trace: fix a few bugs found by staticcheck

First, the regions sort was buggy, as its last comparison was
ineffective.

Second, the insyscall and insyscallRuntime fields were unsigned, so the
check for them being negative was pointless. Make them signed instead,
to also prevent the possibility of underflows when decreasing numbers
that might realistically be 0.

Third, the color constants were all untyped strings except the first
one. Be consistent with their typing.

Change-Id: I4eb8d08028ed92589493c2a4b9cc5a88d83f769b
Reviewed-on: https://go-review.googlesource.com/113895
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/trace/annotations.go

@@ -331,7 +331,7 @@ func analyzeAnnotations() (annotationAnalysisResult, error) {
 			if si != sj {
 				return si < sj
 			}
-			return task.regions[i].lastTimestamp() < task.regions[i].lastTimestamp()
+			return task.regions[i].lastTimestamp() < task.regions[j].lastTimestamp()
 		})
 	}
 	return annotationAnalysisResult{tasks: tasks, regions: regions, gcEvents: gcEvents}, nil

src/cmd/trace/trace.go

@@ -419,9 +419,9 @@ type heapStats struct {
 }
 
 type threadStats struct {
-	insyscallRuntime uint64 // system goroutine in syscall
-	insyscall        uint64 // user goroutine in syscall
-	prunning         uint64 // thread running P
+	insyscallRuntime int64 // system goroutine in syscall
+	insyscall        int64 // user goroutine in syscall
+	prunning         int64 // thread running P
 }
 
 type frameNode struct {
@@ -1010,8 +1010,8 @@ func (ctx *traceContext) emitGoroutineCounters(ev *trace.Event) {
 }
 
 type threadCountersArg struct {
-	Running   uint64
-	InSyscall uint64
+	Running   int64
+	InSyscall int64
 }
 
 func (ctx *traceContext) emitThreadCounters(ev *trace.Event) {
@@ -1203,7 +1203,7 @@ func viewerDataTraceConsumer(w io.Writer, start, end int64) traceConsumer {
 // https://github.com/catapult-project/catapult/blob/master/tracing/tracing/base/color_scheme.html#L50
 // The chrome trace viewer allows only those as cname values.
 const (
-	colorLightMauve     string = "thread_state_uninterruptible" // 182, 125, 143
+	colorLightMauve     = "thread_state_uninterruptible" // 182, 125, 143
 	colorOrange         = "thread_state_iowait"          // 255, 140, 0
 	colorSeafoamGreen   = "thread_state_running"         // 126, 200, 148
 	colorVistaBlue      = "thread_state_runnable"        // 133, 160, 210