milo: buildbucket builer view

common/clock/external.go

Index: common/clock/external.go
diff --git a/common/clock/external.go b/common/clock/external.go
index 35ad09c07da1675438428dd45c679bd182bb984c..781492a9d77adf22e12f62416078fb150982b31d 100644
--- a/common/clock/external.go
+++ b/common/clock/external.go
@@ -60,3 +60,8 @@ func NewTimer(ctx context.Context) Timer {
 func After(ctx context.Context, d time.Duration) <-chan TimerResult {
 	return Get(ctx).After(ctx, d)
 }
+
+// Since is an equivalent of time.Since.
+func Since(ctx context.Context, t time.Time) time.Duration {
+	return Now(ctx).Sub(t)
+}