Log uses of isolate archive and exparchive when 'chromium' build tag is set.

client/cmd/isolate/isolate_event_logger.go

Index: client/cmd/isolate/isolate_event_logger.go
diff --git a/client/cmd/isolate/isolate_event_logger.go b/client/cmd/isolate/isolate_event_logger.go
index 4878f1d4ac7894d542bd00c29f5b8856b5e1cbd9..1d424dc45fd71bf852096580bfb3041cdf2deaaf 100644
--- a/client/cmd/isolate/isolate_event_logger.go
+++ b/client/cmd/isolate/isolate_event_logger.go
@@ -13,8 +13,31 @@ import (
 	"github.com/golang/protobuf/proto"
 	"github.com/luci/luci-go/common/eventlog"
 	logpb "github.com/luci/luci-go/common/eventlog/proto"
+	"github.com/luci/luci-go/common/logging"
 )
 
+// eventlogEndpoint returns a destination URL for eventlogs, based on the contents of
+// the endpointFlag.
+func eventlogEndpoint(ctx context.Context, endpointFlag string) string {
+	switch endpointFlag {
+	case "auto":
+		if autoEventlog() {
+			msg := "Automatically logging usage statistics to %s. If this is not desired, then set --eventlog-endpoint=none"
+			logging.Infof(ctx, msg, eventlog.ProdEndpoint)
+			return eventlog.ProdEndpoint
+		}
+		return ""
+	case "test":
+		return eventlog.TestEndpoint
+	case "prod":
+		return eventlog.ProdEndpoint
+	case "none":
+		return ""
+	default:
+		return endpointFlag
+	}
+}
+
 type syncLogger interface {
 	LogSync(ctx context.Context, events ...*eventlog.ChromeInfraLogEvent) error
 	NewLogEvent(ctx context.Context, eventTime eventlog.TypedTime) *eventlog.ChromeInfraLogEvent
@@ -30,10 +53,11 @@ type IsolateEventLogger struct {
 }
 
 // NewLogger returns an IsolateEventLogger which logs to the specified endpoint.
+// endpoint is the URL to which logs will be sent.
 func NewLogger(ctx context.Context, endpoint string) *IsolateEventLogger {
 	l := &IsolateEventLogger{}
-	if host := eventlogEndpoint(endpoint); host != "" {
-		l.client = eventlog.NewClient(ctx, host)
+	if endpoint != "" {
+		l.client = eventlog.NewClient(ctx, endpoint)
 	}
 	return l
 }
@@ -62,17 +86,6 @@ func (l *IsolateEventLogger) logStats(ctx context.Context, op *logpb.IsolateClie
 	return l.client.LogSync(ctx, event)
 }
 
-func eventlogEndpoint(endpointFlag string) string {
-	switch endpointFlag {
-	case "test":
-		return eventlog.TestEndpoint
-	case "prod":
-		return eventlog.ProdEndpoint
-	default:
-		return endpointFlag
-	}
-}
-
 // buildbotInfo contains information about the build in which this command was run.
 type buildbotInfo struct {
 	// Variables which are not present in the environment are nil.