 
         if requestStarted || responseStarted
             {
-            overallProgress.holdConstant
+            overallProgress = overallProgress.heldConstant
                 { connectLatency.complete() }
             }
         else

    var rawFractionDone: Double
        { return (child.fractionDone - 1) * adjustment + 1 }

    mutating func holdConstant(closure: () -> Void)
        {
        let before = fractionDone
        closure()
        let afterRaw = child.fractionDone
        if afterRaw != 1
            { adjustment = (before - 1) / (afterRaw - 1) }
        }
    }


                { return nil }
            }

        overallProgress = overallProgress.heldConstant
            {
            uploadProgress.actualTotal   = optionalTotal(metrics.requestBytesTotal)
            downloadProgress.actualTotal = optionalTotal(metrics.responseBytesTotal)
