Error occurred in deployment step ‘Activate Features': System.TimeoutException: The HTTP request has timed out after 20000 milliseconds.

I am running SP 2013 dev environment and I recently ran into a problem described in the post title. I tried to deploy a solution with feature activation which included SP 2013 Workflow SPIs. I tried to solve the issue by applying a solution described here but it wasn't helpful in my situation. I already had registry settings set up to extend timeout period for SharePoint deployment.

Visual studio output window might look like this:
  Activating feature 'Feature1' ...
Error occurred in deployment step 'Activate Features': System.TimeoutException: The HTTP request has timed out after 20000 milliseconds. ---> System.Net.WebException: The request was aborted: The request was canceled.
   at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at Microsoft.Workflow.Client.HttpGetResponseAsyncResult`1.OnGotResponse(IAsyncResult result)
   --- End of inner exception stack trace ---
   at Microsoft.Workflow.Common.AsyncResult.End[TAsyncResult](IAsyncResult result)
   at Microsoft.Workflow.Client.Ht

I noticed that I had Fiddler2 running in the background while trying to deploy my solution. I exited Fiddler2 application and tried to deploy again. This time deploy was successful. It very well might be a cause of error. Just to be sure I tried to reproduce the same behavior again by starting Fiddler2 again and trying to deploy the wsp using Visual Studio 2012. This time VS couldn't delete workflows and workflow associations from the site but it was able to deploy successfully. I turned off Fiddler2 again and tried to deploy, and it went smooth, without any errors. I might be wrong but it seems to me that Fiddler's proxy is interfering with deployment of workflows.

I know there are many reasons causing this error but this solution helped me. Hopefully it helps someone else.