misc/dashboard/codereview: interpret zero reviewers as the CL being closed.

This is the state when the CL has been submitted by someone other than
the CL author, but before the CL author has synched their client.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6458044

misc/dashboard/codereview/dashboard/cl.go

@@ -295,6 +295,7 @@ func updateCL(c appengine.Context, n string) error {
 
 	var apiResp struct {
 		Description string   `json:"description"`
+		Reviewers   []string `json:"reviewers"`
 		Created     string   `json:"created"`
 		OwnerEmail  string   `json:"owner_email"`
 		Modified    string   `json:"modified"`
@@ -334,6 +335,13 @@ func updateCL(c appengine.Context, n string) error {
 	if i := strings.Index(cl.FirstLine, "\n"); i >= 0 {
 		cl.FirstLine = cl.FirstLine[:i]
 	}
+	// Treat zero reviewers as a signal that the CL is completed.
+	// This could be after the CL has been submitted, but before the CL author has synced,
+	// but it could also be a CL manually edited to remove reviewers.
+	if len(apiResp.Reviewers) == 0 {
+		cl.Closed = true
+	}
+
 	lgtm := make(map[string]bool)
 	notLGTM := make(map[string]bool)
 	rcpt := make(map[string]bool)