Added no-cache header to HTTP GET command of RemoteWebDriver

When Selenium RemoteWebDriver is connecting to Selenium Server
(e.g. SauceLabs) through HTTP proxy, same/repetitive HTTP commands
can be cached by the proxy. This leads to unexpected and unwanted
behavior that HTTP commands return cached and outdated data from the
server (e.g. screenshots).

To fix this I have added Cache-Control: no-cache HTTP header.

Selenium Java implementation has this fix for a while – at least from
version 2.26.

Fixes #5404

Signed-off-by: Jim Evans <james.h.evans.jr@gmail.com>

dotnet/src/webdriver/Remote/HttpCommandExecutor.cs

@@ -163,6 +163,10 @@ private HttpResponseInfo MakeHttpRequest(HttpRequestInfo requestInfo)
                 requestStream.Write(data, 0, data.Length);
                 requestStream.Close();
             }
+            else if (request.Method == CommandInfo.GetCommand)
+            {
+                request.Headers.Add("Cache-Control", "no-cache");
+            }
 
             HttpResponseInfo responseInfo = new HttpResponseInfo();
             HttpWebResponse webResponse = null;