Reenable BrowserGuestSessionNavigatorTest.Browser_Gets_Created_On_Visiting_Desktop

TaskManager rewrite fixed the assert failure hit by this test. It no longer
needs to be disbled.

TBR=pkasting@chromium.org
BUG=469717

Change-Id: Ifcd406a631953491123792fa61caaf5628d52223
Reviewed-on: https://chromium-review.googlesource.com/663303Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501518}

chrome/browser/ui/browser_navigator_browsertest_chromeos.cc

@@ -99,10 +99,8 @@ IN_PROC_BROWSER_TEST_F(BrowserGuestSessionNavigatorTest,
 
 // Test that in multi user environments a newly created browser gets created
 // on the same desktop as the browser is shown on.
-//
-// Flakily hits assert: http://crbug.com/469717
 IN_PROC_BROWSER_TEST_F(BrowserGuestSessionNavigatorTest,
-                       DISABLED_Browser_Gets_Created_On_Visiting_Desktop) {
+                       Browser_Gets_Created_On_Visiting_Desktop) {
   // Test 1: Test that a browser created from a visiting browser will be on the
   // same visiting desktop.
   {