Update chromeos system menu buttons for MD.

ash/common/system/tray/tray_utils.h

Index: ash/common/system/tray/tray_utils.h
diff --git a/ash/common/system/tray/tray_utils.h b/ash/common/system/tray/tray_utils.h
index beb89876031cebef18f24d76dc02550ea0dcab54..d1b869dab58f5ee57a3be419277da7145ffc6c6c 100644
--- a/ash/common/system/tray/tray_utils.h
+++ b/ash/common/system/tray/tray_utils.h
@@ -12,7 +12,9 @@
 #include "base/strings/string16.h"
 
 namespace views {
+class ButtonListener;
 class Label;
+class LabelButton;
 class Separator;
 class View;
 }
@@ -21,6 +23,18 @@ namespace ash {
 
 class TrayItemView;
 
+// Creates a button for use in the system menu that only has a visible border
+// when being hovered/clicked. Caller assumes ownership.
+views::LabelButton* CreateTrayPopupBorderlessButton(
+    views::ButtonListener* listener,
+    const base::string16& text);
+
+// Creates a button for use in the system menu. For MD, this is a prominent text
+// button. For non-MD, this does the same thing as the above. Caller assumes
+// ownership.
+views::LabelButton* CreateTrayPopupButton(views::ButtonListener* listener,
+                                          const base::string16& text);
+
 // Sets up a Label properly for the tray (sets color, font etc.).
 void SetupLabelForTray(views::Label* label);