Fix exception on network retry.

The numBytesRemainingObj parameter in |NetworkingEngine.send_| was
optional, but in some circumstances we were assuming that it was set.
This just changes the parameter to be non-optional.
In fact, the parameter now being non-optional revealed an error that
caused the numBytesRemainingObj to be lost on network retry.

Fixes #1930

Change-Id: I74f24309f859f975f51e20455739b806ed3f4ecd

lib/net/networking_engine.js

@@ -452,7 +452,7 @@ shaka.net.NetworkingEngine.prototype.makeRequestWithRetry_ =
  * @param {!shaka.net.Backoff} backoff
  * @param {number} index
  * @param {?shaka.util.Error} lastError
- * @param {shaka.net.NetworkingEngine.NumBytesRemainingClass=}
+ * @param {shaka.net.NetworkingEngine.NumBytesRemainingClass}
  *     numBytesRemainingObj
  * @return {!shaka.extern.IAbortableOperation.<
  *               shaka.net.NetworkingEngine.ResponseAndGotProgress>}
@@ -547,7 +547,8 @@ shaka.net.NetworkingEngine.prototype.send_ = function(
       // Move to the next URI.
       index = (index + 1) % request.uris.length;
       const shakaError = /** @type {shaka.util.Error} */(error);
-      return this.send_(type, request, backoff, index, shakaError);
+      return this.send_(type, request, backoff, index, shakaError,
+                        numBytesRemainingObj);
     }
 
     // The error was not recoverable, so do not try again.