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

ash/common/system/chromeos/palette/palette_tray.h

Index: ash/common/system/chromeos/palette/palette_tray.h
diff --git a/ash/common/system/chromeos/palette/palette_tray.h b/ash/common/system/chromeos/palette/palette_tray.h
index dcd387cffe49a9b222d434747f214f47bff24da3..73856620b60043b9b69827d5ad991c5d1313f3fc 100644
--- a/ash/common/system/chromeos/palette/palette_tray.h
+++ b/ash/common/system/chromeos/palette/palette_tray.h
@@ -24,6 +24,7 @@ namespace ash {
 
 class TrayBubbleWrapper;
 class PaletteToolManager;
+class ViewObserver;
 
 // The PaletteTray shows the palette in the bottom area of the screen. This
 // class also controls the lifetime for all of the tools available in the
@@ -34,7 +35,7 @@ class ASH_EXPORT PaletteTray : public TrayBackgroundView,
                                public PaletteToolManager::Delegate,
                                public views::TrayBubbleView::Delegate {
  public:
-  explicit PaletteTray(WmShelf* wm_shelf);
+  explicit PaletteTray(WmShelf* wm_shelf, ViewObserver* view_observer);
   ~PaletteTray() override;
 
   // ActionableView: