Bug 499438, focus window so that test_close_download_manager.xul doesn't fail on Linux, r=sdwlish

toolkit/mozapps/downloads/tests/chrome/test_close_download_manager.xul

@@ -108,6 +108,7 @@ function runTest()
   let testObs = {
     observe: function(aSubject, aTopic, aData) {
       let win = aSubject.QueryInterface(Ci.nsIDOMWindow);
+      win.focus();
       switch(testPhase++) {
         case 0:
           testCloseDMWithEscKey(win);