Make sure Ruby properly kills Firefox process if silent startup times out.

Thanks to birtic for the patch.
Fixes issue 7392.

Author: jarib

rb/CHANGES

@@ -1,3 +1,9 @@
+2.43.0 (???)
+============
+
+* Firefox
+  - Make sure browser process is properly killed if silent startup hangs (#7392)
+
 2.42.0 (2014-05-23)
 ===================
 

rb/lib/selenium/webdriver/firefox/binary.rb

@@ -44,7 +44,14 @@ def quit
         end
 
         def wait
-          @process.poll_for_exit(WAIT_TIMEOUT) if @process
+          return unless @process
+
+          begin
+            @process.poll_for_exit(WAIT_TIMEOUT)
+          rescue ChildProcess::TimeoutError => e
+            @process.stop
+            raise e
+          end
         end
 
         private