Fix a couple issues with sticky headers

ash/common/system/tray/tray_popup_utils.cc

Index: ash/common/system/tray/tray_popup_utils.cc
diff --git a/ash/common/system/tray/tray_popup_utils.cc b/ash/common/system/tray/tray_popup_utils.cc
index 69050a7d944225076d23ceda2e2499a2e9750026..60f36e275f7151a16d0d0d4a0c1777769d9d9b52 100644
--- a/ash/common/system/tray/tray_popup_utils.cc
+++ b/ash/common/system/tray/tray_popup_utils.cc
@@ -5,6 +5,7 @@
 #include "ash/common/system/tray/tray_popup_utils.h"
 
 #include "ash/common/ash_constants.h"
+#include "ash/common/ash_view_ids.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/system/tray/fixed_sized_image_view.h"
@@ -14,6 +15,7 @@
 #include "ash/common/system/tray/tray_popup_label_button_border.h"
 #include "ash/common/wm_shell.h"
 #include "ui/views/animation/ink_drop_impl.h"
+#include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/controls/button/label_button.h"
@@ -220,6 +222,14 @@ views::Slider* TrayPopupUtils::CreateSlider(views::SliderListener* listener) {
   return slider;
 }
 
+void TrayPopupUtils::ConfigureAsStickyHeader(views::View* view) {
+  view->set_id(VIEW_ID_STICKY_HEADER);
+  view->set_background(
+      views::Background::CreateSolidBackground(kBackgroundColor));
+  view->SetBorder(
+      views::CreateEmptyBorder(gfx::Insets(kMenuSeparatorVerticalPadding, 0)));
+}
+
 void TrayPopupUtils::ConfigureContainer(TriView::Container container,
                                         views::View* container_view) {
   container_view->SetLayoutManager(