title: Selenium does not download file as configured
body: <p>I'm trying to configure selenium to download files to my download dir, but seems like it always downloads to a different folder.</p>
  
  <p>Here is the code I'm using to configure firefox webdriver:</p>
  
  <pre><code>FirefoxProfile profile = new FirefoxProfile();
  profile.setPreference("browser.helperApps.neverAsk.saveToDisk",
    "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;");
  profile.setPreference("browser.download.manager.showWhenStarting", false);
  profile.setPreference("pdfjs.disabled", true);
  profile.setAcceptUntrustedCertificates(true);
  profile.setAssumeUntrustedCertificateIssuer(false);
  profile.setPreference("browser.download.folderList", 2);
  profile.setPreference("browser.tabs.remote.autostart.2", false);
  profile.setPreference("browser.download.dir", System.getProperty("user.home") + "\\Downloads\\");
  </code></pre>
  
  <p>Yet every time I run my test, my test fails because it can't find the file and I get this on the log:</p>
  
  <pre><code>1505401302370   addons.productaddons    INFO    Completed downloading document
  1505401303224   addons.productaddons    INFO    downloadXHR File download. status=200
  1505401303226   addons.productaddons    INFO    Downloaded file will be saved to C:\Users\MYUSER\AppData\Local\Temp\tmpaddon
  </code></pre>
  
  <p>Am I missing something here?</p>
  
  <p>[UPDATE]</p>
  
  <p>I'm using geckodriver v0.18.0 and firefox version 55.0.3</p>