Clean up some ash constants.

ash/system/session/logout_button_tray.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/system/session/logout_button_tray.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/public/cpp/shelf_types.h"
@@ skipping 24 matching lines @@
 
 LogoutButtonTray::LogoutButtonTray(WmShelf* wm_shelf)
     : TrayBackgroundView(wm_shelf, false),
       button_(nullptr),
       login_status_(LoginStatus::NOT_LOGGED_IN),
       show_logout_button_in_tray_(false) {
   views::MdTextButton* button =
       views::MdTextButton::Create(this, base::string16());
   button->SetProminent(true);
   button->SetBgColorOverride(gfx::kGoogleRed700);
-  // Base font size + 2 = 14.
-  // TODO(estade): should this 2 be shared with other tray views? See
-  // crbug.com/623987
-  button->AdjustFontSize(2);
+  button->AdjustFontSize(kTrayTextFontSizeIncrease);
   button_ = button;
 
   // Since LogoutButtonTray has a red background and it is distinguished
   // by itself, no separator is needed on its right side.
   set_separator_visibility(false);
   tray_container()->AddChildView(button_);
   Shell::Get()->system_tray_notifier()->AddLogoutButtonObserver(this);
 }
 
 LogoutButtonTray::~LogoutButtonTray() {
@@ skipping 64 matching lines @@
     button_->SetText(base::string16());
     button_->SetAccessibleName(title);
     button_->SetImage(views::LabelButton::STATE_NORMAL,
                       gfx::CreateVectorIcon(kShelfLogoutIcon, kTrayIconColor));
     button_->SetMinSize(gfx::Size(kTrayItemSize, kTrayItemSize));
   }
   UpdateVisibility();
 }
 
 }  // namespace ash