I'm using the webview tag in chromium and I want to capture the html requests. Unfortunately webview does not support proxies. Is there any way I can just do a normal http request to fiddler at localhost:8888 and somehow put the real destination in the URL? Maybe something like http://localhost:8888?url=google.com?
I'm not clear on which Chromium you're using, but generally I'd expect that it should adopt the OS proxy settings, and if it doesn't, that's a bug that should get filed.
Yes, you can send Web Requests directly to Fiddler using the technique you describe, but the cookies and security permissions aren't likely to work correctly.