Milo: Add LogDog annotation stream support.

common/proto/milo/annotations.proto

 // Copyright (c) 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.
 
 syntax = "proto3";
 
 package milo;
 
 import "google/protobuf/timestamp.proto";
 
 // Status is the expressed root step of this step or substep.
 enum Status {
   // The step is still running.
   RUNNING = 0;
   // The step has finished successfully.
   SUCCESS = 1;
   // The step has finished unsuccessfully.
   FAILURE = 2;
+  // The step has been scheduled, but not yet started.
+  PENDING = 3;
 }
 
 // FailureType provides more details on the nature of the Status.
 message FailureDetails {
   // Type is the type of failure.
   enum Type {
     // The failure is a general failure.
     GENERAL = 0;
     // An unhandled exception occured during execution.
     EXCEPTION = 1;
     // The failure is related to a failed infrastructure component, not an error
     // with the Step itself.
     INFRA = 2;
     // The failure is due to a failed Dungeon Master dependency. This should be
     // used if a Step's external depdendency fails and the Step cannot recover
     // or proceed without it.
     DM_DEPENDENCY_FAILED = 3;
+    // The step was cancelled.
+    CANCELLED = 4;
   }
   Type type = 1;
 
   // An optional string describing the failure.
   string text = 2;
 
   // If the failure type is DEPENDENCY_FAILED, the failed dependencies should be
   // listed here.
   repeated DMLink failed_dm_dependency = 3;
 }
@@ skipping 136 matching lines @@
 
   // The quest name.
   string quest = 2;
 
   // The attempt number.
   int64 attempt = 3;
 
   // The execution number.
   int64 execution = 4;
 }