Feature Request: Add arbitrary HTTP headers to requests made by the browser

As a WebDriver user, I want to add arbitrary HTTP headers to the requests made by the browser so that I can change how the web servers I am testing handle the requests.

My use case is that I have a pool of servers behind a NAT firewall that distributes HTTP requests to individual servers. I have configured the firewall so that if there is an X-Specific-Host header with a specific pool hostname, the request will be routed to that specific host so that I can test that specific host.

The workaround is to use a proxy, but this affects SSL.

How I envision this working is much like cookies, there would be a host/path table (where all paths below the configured path would match) that includes a header name and value, and if the request is to be sent to a matching host/path, the browser will add the header and value to the request.

I don't know enough about the internals of WebDriver to know how best to specify these, but I can see several operations required that WebDriver would need to accept and pass on to the browser (which would also need to accept and handle it):

• ArbitraryHeaders.Add(string Hostname, string Path, string HeaderName, string HeaderValue);
• ArbitraryHeaders.Delete(string Hostname, string Path, string HeaderName);
• ArbitraryHeaders.List(); (Returns all configured arbitrary headers)
• ArbitraryHeaders.Get(string Hostname, string Path, string HeaderName); (Returns a single arbitrary header)
• A way to query whether this is supported by the browser and return a boolean value.

Start by reviewing the WebDriver protocol and the requested ArbitraryHeaders operations described in the issue. Done would require an agreed specification for host/path matching, header management, and browser support detection; no repository files or tests are identified.