Steps to reproduce:
1. Open the attached project (UWPFiddlerRepro.zip)
2. Switch platform to Windows Store
3. Build for WSA Universal 10 (.NET backend), Build type - XAML, Enable C# projects, Enable Development build, Enable Copy references
4. Open Visual Studio solution
5. Deploy on local machine (DEBUG)
6. Set up Fiddler to trace requests on your PC
7. Use the WinConfig option in Fiddler to enable loopback exemptions so you can see UWP web traffic (you may need to restart Fiddler)
8. Press any key to send a request to 'www.google.com'
9. Observe that the request to www.google.com initiated from the Unity WWW request does not appear in Fiddler

Expected result: WWW request should appear in Fiddler
Actual result: WWW request does not appear in Fiddler

Reproduced with: 5.5.4f1, 5.6.1p2, 2017.1.0b8
Not reproduced with: 5.5.1f1