We expect the route response to come back with an error, at which point the spinner will be cleared from the UI.  So it sounds more like the route response isn't coming back for some reason.

Talked to Vadim. The route response is resolved with a nondisplay route, but later the route creation fails and an issue is sent back from MRP to MR. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/813d605e717ff246ea1bf65e11db6fbb4cf8679e

commit 813d605e717ff246ea1bf65e11db6fbb4cf8679e
Author: apacible <apacible@chromium.org>
Date: Tue Mar 22 19:36:00 2016

[Media Router WebUI] Clear pending route creation properties on error.

Sometimes, routes are created but initially "not for display". These are later resolved as "for display", then updated with an updated route list from the MRP to the WebUI.

Currently, when a route fails to resolve "for display", an issue is sent to the WebUI but no indication that the route creation had failed. This causes the sink that is currently "pending route launch" to show the spinner forever, rendering the rest of the sink list unable to create a route.

This change corresponds with a change in the MRP that makes use of the |routeId| field in an incoming issue and clears any pending route creation properties if the error corresponds to |pendingCreatedRouteId_|. This also renames |mediaRouteId| to |routeId| to be uniform with other references.

BUG= 592081 

Review URL: https://codereview.chromium.org/1807223003

Cr-Commit-Position: refs/heads/master@{#382640}

[modify] https://crrev.com/813d605e717ff246ea1bf65e11db6fbb4cf8679e/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
[modify] https://crrev.com/813d605e717ff246ea1bf65e11db6fbb4cf8679e/chrome/browser/resources/media_router/media_router_data.js