dispatcher: fix test result parsing, build ranges for failure alerts, other fixes

go/src/infra/monitoring/messages/gatekeeper.go

Index: go/src/infra/monitoring/messages/gatekeeper.go
diff --git a/go/src/infra/monitoring/messages/gatekeeper.go b/go/src/infra/monitoring/messages/gatekeeper.go
index 8cc8d41b5d731883c6f2e52994d591a08a4208e1..8ba9eca0fdd1a6a9e66fc65b9c642ee6c848b383 100644
--- a/go/src/infra/monitoring/messages/gatekeeper.go
+++ b/go/src/infra/monitoring/messages/gatekeeper.go
@@ -27,3 +27,9 @@ type BuilderConfig struct {
 	ClosingSteps      []string `json:"closing_steps"`
 	ClosingOptional   []string `json:"closing_optional"`
 }
+
+// TreeMasterConfig is a named group of masters. e.g. chromium, or blink.
+type TreeMasterConfig struct {
+	BuildDB string   `json:"build-db"`
+	Masters []string `json:"masters"`
+}