[Chrome OS MD] Draw a 1px separator between 2 tray items

ash/common/shelf/wm_shelf_observer.h

Index: ash/common/shelf/wm_shelf_observer.h
diff --git a/ash/common/shelf/wm_shelf_observer.h b/ash/common/shelf/wm_shelf_observer.h
index 2fd43598530fa6e2a3eca9efeb0b933c929d25a8..e3c3b35aa50fa3f35f57a1f3740ef332bb2bece1 100644
--- a/ash/common/shelf/wm_shelf_observer.h
+++ b/ash/common/shelf/wm_shelf_observer.h
@@ -10,6 +10,7 @@
 #include "ash/common/wm/background_animator.h"
 
 namespace ash {
+class TrayBackgroundView;
 
 // Used to observe changes to the shelf.
 class ASH_EXPORT WmShelfObserver {
@@ -20,6 +21,7 @@ class ASH_EXPORT WmShelfObserver {
   virtual void WillChangeVisibilityState(ShelfVisibilityState new_state) {}
   virtual void OnAutoHideStateChanged(ShelfAutoHideState new_state) {}
   virtual void OnShelfIconPositionsChanged() {}
+  virtual void OnVisibilityChange(TrayBackgroundView* tray) {}

[James Cook, 2016/08/09 00:25:17]

nit: Document what this does / when it will be called.

Also, I would name the method something that has "tray" in it, like
OnTrayVisibilityChanging() or similar.  Also, if it's called after the change,
call it "Changed". If before, call it "Changing".

[yiyix, 2016/08/11 01:23:18]

Done.

 
  protected:
   virtual ~WmShelfObserver() {}