Disable flaky test.

appengine/cmd/dm/deps/walk_graph_test.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.
 
 package deps
 
 import (
         "fmt"
         "testing"
         "time"
@@ skipping 377 matching lines @@
                                                                                 1: {Id: dm.NewAttemptID(x, 1)},
                                                                                 2: {Id: dm.NewAttemptID(x, 2)},
                                                                         },
                                                                 },
                                                         },
                                                 })
                                         })
 
                                 })
 
-                                Convey("early stop", func() {
+                                // This is disabled beacuse it was flaky.
+                                // BUG: crbug.com/621170
+                                SkipConvey("early stop", func() {
                                         req.Limit.MaxDepth = 100
                                         req.Limit.MaxTime = google_pb.NewDuration(time.Nanosecond)
                                         tc := clock.Get(c).(testclock.TestClock)
                                         tc.SetTimerCallback(func(d time.Duration, t clock.Timer) {
                                                 tc.Add(d + time.Second)
                                         })
                                         ret, err := newDecoratedDeps().WalkGraph(c, req)
                                         So(err, ShouldBeNil)
                                         So(ret.HadMore, ShouldBeTrue)
                                 })
 
                         })
                 })
         })
 }