tileLoadProgressEvent will not be called if connection is timed out

I am trying to get the viewer’s canvas image by returning a callback to a function when tileLoadProgressEvent has reached 0. However, if there’s a connection timed out, the tileLoadProgressEvent will not be called again.

Start by tracing the viewer's tileLoadProgressEvent handling and reproduce the behavior with a connection timeout. The issue is resolved when the event is called again after the timed-out tile load, allowing a callback waiting for progress to reach 0 to run.

Written by the indexing model from the issue text.