Created attachment 14121 [details]
Repro part 1
It looks like there is a memory leak in HttpClient when using Ntlm authentication. HttpClient seems to work ok if no credentials are used, but when request is authorized (server responds with 200 OK) memory starts to climb.
Attached is a sample app, which makes a connection to the server we have set up (code for the server is also included). We will remove the server in a week, but wanted to make it easy to test for somebody willing to help.
The app is a console app, few lines of code which just makes a connection and checks that response is 200 OK.
If you let it run for a couple of minutes you should see memory rise.
To try, open HttpClientMemoryLeak.zip in Xamarin studio and run (it will make a connection to a server we have set up). You can also run your own server.
Created attachment 14122 [details]
Repro part 2
Created attachment 14123 [details]
Real repro part 2
Repro web server requires asp.net, which I do not have access to a windows dev box to validate.
Fixed in master