slog: remove disableSourceLine

Remove an obsolete way of disabling PC fetching for benchmarks.
Now we do it with the nopc build tag.

Change-Id: I7e6666ed1692ccf08388ea697a8a03b3e4149703
Reviewed-on: https://go-review.googlesource.com/c/exp/+/442358
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>

Author: jba

slog/logger.go

@@ -126,16 +126,8 @@ func (l *Logger) LogDepth(calldepth int, level Level, msg string, args ...any) {
 	_ = l.Handler().Handle(r)
 }
 
-var useSourceLine = true
-
-// Temporary, for benchmarking.
-// Eventually, getting the pc should be fast.
-func disableSourceLine() { useSourceLine = false }
-
 func (l *Logger) makeRecord(msg string, level Level, depth int) Record {
-	if useSourceLine {
-		depth += 5
-	}
+	depth += 5
 	return NewRecord(time.Now(), level, msg, depth)
 }
 

slog/logger_test.go

@@ -334,7 +334,6 @@ func (h discardHandler) WithScope(name string) Handler {
 // This is a simple benchmark. See the benchmarks subdirectory for more extensive ones.
 func BenchmarkNopLog(b *testing.B) {
 	b.ReportAllocs()
-	disableSourceLine()
 	l := New(&captureHandler{})
 	b.Run("attrs", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {