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

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

Index: ash/common/system/chromeos/palette/palette_tray.cc
diff --git a/ash/common/system/chromeos/palette/palette_tray.cc b/ash/common/system/chromeos/palette/palette_tray.cc
index d28e7f7addf7e8ff3b634992673e8953730f8d83..6c1eae281c3c04c3011a30ff1e0f800faaced206 100644
--- a/ash/common/system/chromeos/palette/palette_tray.cc
+++ b/ash/common/system/chromeos/palette/palette_tray.cc
@@ -8,6 +8,7 @@
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/wm_shelf.h"
+#include "ash/common/shelf/wm_shelf_observer.h"
 #include "ash/common/shelf/wm_shelf_util.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/system/chromeos/palette/palette_tool.h"
@@ -103,8 +104,8 @@ views::View* CreateTitleView() {
 
 }  // namespace
 
-PaletteTray::PaletteTray(WmShelf* wm_shelf)
-    : TrayBackgroundView(wm_shelf),
+PaletteTray::PaletteTray(WmShelf* wm_shelf, WmShelfObserver* wm_shelf_observer)
+    : TrayBackgroundView(wm_shelf, wm_shelf_observer),
       palette_tool_manager_(new PaletteToolManager(this)) {
   PaletteTool::RegisterToolInstances(palette_tool_manager_.get());