Grid Nodes can set firefox binary paths

This has been a bug since before 3.0 was released, and
this now restores the original behaviour we had in
2.53.1.

Of course, this behaviour is All Wrong, as it doesn't
bother to update FirefoxOptions, and it should be the
Node that performs this translation, not the Hub, but
you win some, you lose some.

Author: shs96c

java/server/src/org/openqa/grid/web/servlet/handler/RequestHandler.java

@@ -17,6 +17,8 @@
 
 package org.openqa.grid.web.servlet.handler;
 
+import com.google.common.collect.ImmutableMap;
+
 import org.openqa.grid.common.exception.ClientGoneException;
 import org.openqa.grid.common.exception.GridException;
 import org.openqa.grid.internal.ExternalSessionKey;
@@ -27,6 +29,7 @@
 import org.openqa.grid.internal.exception.NewSessionException;
 import org.openqa.grid.internal.listeners.TestSessionListener;
 import org.openqa.selenium.remote.DesiredCapabilities;
+import org.openqa.selenium.remote.NewSessionPayload;
 
 import java.io.IOException;
 import java.net.SocketTimeoutException;
@@ -79,7 +82,11 @@ public  RequestHandler(
    */
   public void forwardNewSessionRequestAndUpdateRegistry(TestSession session)
       throws NewSessionException {
-    try {
+    try (NewSessionPayload payload = NewSessionPayload.create(
+        ImmutableMap.of("desiredCapabilities", session.getRequestedCapabilities()))) {
+      StringBuilder json = new StringBuilder();
+      payload.writeTo(json);
+      request.setBody(payload.toString());
       session.forward(getRequest(), getResponse(), true);
     } catch (IOException e) {
       //log.warning("Error forwarding the request " + e.getMessage());