Don't animate the default/background layer if there is no background.

chrome/browser/chromeos/login/base_login_display_host.cc

Index: chrome/browser/chromeos/login/base_login_display_host.cc
diff --git a/chrome/browser/chromeos/login/base_login_display_host.cc b/chrome/browser/chromeos/login/base_login_display_host.cc
index 9e44d640999582798342cdcdb0273b4fd98fb46f..4401d7534cc5328cad0ae25b514a01bfbc379c5b 100644
--- a/chrome/browser/chromeos/login/base_login_display_host.cc
+++ b/chrome/browser/chromeos/login/base_login_display_host.cc
@@ -363,8 +363,10 @@ void BaseLoginDisplayHost::StartAnimation() {
         background_transition.release());
   }
 
-  // Browser windows layer opacity animation.
-  if (kEnableBrowserWindowsOpacityAnimation) {
+  // Browser windows layer opacity animation.  Don't fade in the
+  // browser in compact mode because there is nothing behind it.
+  if (kEnableBrowserWindowsOpacityAnimation &&
+      !ash::Shell::GetInstance()->IsWindowModeCompact()) {
     scoped_ptr<ui::LayerAnimationElement> browser_opacity_animation_initial(
         ui::LayerAnimationElement::CreateOpacityElement(
             0.0f,