Add views::Button style enum for LabelButton [native] styling, etc.

ash/system/user/tray_user.cc

Index: ash/system/user/tray_user.cc
diff --git a/ash/system/user/tray_user.cc b/ash/system/user/tray_user.cc
index b7564bd02741ffcaf24d909a9734d0a56263d0d9..44a093edb81c033a9db451a21f14ed00f0921c97 100644
--- a/ash/system/user/tray_user.cc
+++ b/ash/system/user/tray_user.cc
@@ -487,13 +487,13 @@ void UserView::AddLogoutButton(ash::user::LoginStatus login) {
   if (login == ash::user::LOGGED_IN_PUBLIC) {
     TrayPopupLabelButtonBorder* border =
         static_cast<TrayPopupLabelButtonBorder*>(logout_button_->border());
-    border->SetPainter(views::CustomButton::STATE_NORMAL,
+    border->SetPainter(views::Button::STATE_NORMAL,
                        views::Painter::CreateImageGridPainter(
                            kPublicAccountLogoutButtonBorderImagesNormal));
-    border->SetPainter(views::CustomButton::STATE_HOVERED,
+    border->SetPainter(views::Button::STATE_HOVERED,
                        views::Painter::CreateImageGridPainter(
                            kPublicAccountLogoutButtonBorderImagesHovered));
-    border->SetPainter(views::CustomButton::STATE_PRESSED,
+    border->SetPainter(views::Button::STATE_PRESSED,
                        views::Painter::CreateImageGridPainter(
                            kPublicAccountLogoutButtonBorderImagesHovered));
   }