Enable hide animation for login screen.

chrome/browser/chromeos/login/lock_window_aura.cc

Index: chrome/browser/chromeos/login/lock_window_aura.cc
diff --git a/chrome/browser/chromeos/login/lock_window_aura.cc b/chrome/browser/chromeos/login/lock_window_aura.cc
index 4fc118867778a40ae4adc72dee1d333d0709c477..34fec28163584cf876de16405c837c67f730c22f 100644
--- a/chrome/browser/chromeos/login/lock_window_aura.cc
+++ b/chrome/browser/chromeos/login/lock_window_aura.cc
@@ -6,6 +6,7 @@
 
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
+#include "ash/wm/window_animations.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 
@@ -47,6 +48,8 @@ void LockWindowAura::Init() {
   ash::Shell::GetInstance()->GetContainer(
       ash::internal::kShellWindowId_LockScreenContainer)->
       AddChild(GetNativeView());
+  ash::SetWindowVisibilityAnimationTransition(GetNativeView(),
+                                              ash::ANIMATE_NONE);
 }
 
 }  // namespace chromeos