Remove some pre-md code from TrayPopupUtils and UserView.

ash/common/system/tray/tray_popup_utils.h

Index: ash/common/system/tray/tray_popup_utils.h
diff --git a/ash/common/system/tray/tray_popup_utils.h b/ash/common/system/tray/tray_popup_utils.h
index 1e73c1fcce19d71fb0614543b9a7b9ca7af28b3c..ecec2227b9618b85c8cbc0315ec7c4be3eb0b3ce 100644
--- a/ash/common/system/tray/tray_popup_utils.h
+++ b/ash/common/system/tray/tray_popup_utils.h
@@ -15,6 +15,7 @@
 
 namespace views {
 class ButtonListener;
+class CustomButton;
 class ImageView;
 class InkDrop;
 class InkDropRipple;
@@ -113,6 +114,9 @@ class TrayPopupUtils {
   // Creates a default focus painter used for most things in tray popups.
   static std::unique_ptr<views::Painter> CreateFocusPainter();
 
+  // Common setup for various buttons in the system menu.
+  static void ConfigureTrayPopupButton(views::CustomButton* button);
+
   // Sets up |view| to be a sticky header in a tray detail scroll view.
   static void ConfigureAsStickyHeader(views::View* view);