milo: fix build/step timing

appengine/cmd/milo/resp/build.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 //go:generate stringer -type=Status,ComponentType
 
 package resp
 
 import (
         "encoding/json"
@@ skipping 121 matching lines @@
 
         // DependencyFailure if the component has finished incompletely due to a failure in a
         // dependency.
         DependencyFailure // 100 Amber
 
         // WaitingDependency if the component has finished or paused execution due to an
         // incomplete dep.
         WaitingDependency // 100 Brown
 )
 
+// Terminal returns true if the step status won't change.
+func (s Status) Terminal() bool {
+        switch s {
+        case Success, Failure, InfraFailure, Warning, DependencyFailure:
+                return true
+        default:
+                return false
+        }
+}
+
 // MarshalJSON renders enums into String rather than an int when marshalling.
 func (s Status) MarshalJSON() ([]byte, error) {
         return json.Marshal(s.String())
 }
 
 // ComponentType is the type of build component.
 type ComponentType int
 
 const (
         // Recipe corresponds to a full recipe run.  Dependencies are recipes.
@@ skipping 95 matching lines @@
 
         // An icon for the link.  Not compatible with label.  Rendered as <img>
         Img string
 
         // The destination for the link, stuck in a <a href> tag.
         URL string
 
         // Alt text for the image, only supported with img.
         Alt string
 }