dispatcher: updates go/infra/monitoring/messages to parse some more json formats

go/src/infra/monitoring/messages/alerts.go

Index: go/src/infra/monitoring/messages/alerts.go
diff --git a/go/src/infra/monitoring/messages/alerts.go b/go/src/infra/monitoring/messages/alerts.go
index 69a884290ed33725cceafddb631d50c4db1fff6d..c9dcdc1bf91c1c118beaea5c7f2b8974a35387e1 100644
--- a/go/src/infra/monitoring/messages/alerts.go
+++ b/go/src/infra/monitoring/messages/alerts.go
@@ -76,13 +76,14 @@ type Link struct {
 
 // BuildFailure is an Extension.
 type BuildFailure struct {
-	Builders         []Builder
+	TreeCloser       bool
+	Builders         []AlertedBuilder
 	Reasons          []Reason
 	RegressionRanges []RegressionRange `json:"regression_ranges"`
 }
 
-// Builder represents an individual builder.
-type Builder struct {
+// AlertedBuilder represents an individual builder.
+type AlertedBuilder struct {
 	Name          string
 	URL           string
 	FirstFailure  EpochTime `json:"first_failure"`