Makes workspace 2 show an alternate background (system background)

ash/wm/window_animations.h

Index: ash/wm/window_animations.h
diff --git a/ash/wm/window_animations.h b/ash/wm/window_animations.h
index 9ddbbaceefc4dd8ebc75d53f00b148d8dcb4f827..60f63ebac0a2489f4adb2abe24bd633e51fb6c6f 100644
--- a/ash/wm/window_animations.h
+++ b/ash/wm/window_animations.h
@@ -108,6 +108,9 @@ ASH_EXPORT void AnimateWorkspaceIn(aura::Window* window,
 ASH_EXPORT void AnimateWorkspaceOut(aura::Window* window,
                                     WorkspaceAnimationDirection direction);
 
+// Returns the amount of time before destroying the system background.
+ASH_EXPORT base::TimeDelta GetSystemBackgroundDestroyDuration();
+
 namespace internal {
 
 // Returns the duration of the cross-fade animation based on the |old_bounds|