Use views::style for buttons, bootstrap ash_typography to do so.

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 "ash/public/cpp/ash_typography.h"
 #include "ash/resources/vector_icons/vector_icons.h"
 #include "ash/shelf/wm_shelf.h"
 #include "ash/shell.h"
 #include "ash/system/session/logout_confirmation_controller.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/system_tray_controller.h"
 #include "ash/system/tray/system_tray_notifier.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_container.h"
 #include "ash/system/user/login_status.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/paint_vector_icon.h"
 #include "ui/views/controls/button/md_text_button.h"
 #include "ui/views/layout/fill_layout.h"
 
 namespace ash {
 
 LogoutButtonTray::LogoutButtonTray(WmShelf* wm_shelf)
     : wm_shelf_(wm_shelf),
       container_(new TrayContainer(wm_shelf)),
-      button_(views::MdTextButton::Create(this, base::string16())),
+      button_(views::MdTextButton::Create(this,
+                                          base::string16(),
+                                          CONTEXT_LAUNCHER_BUTTON)),
       show_logout_button_in_tray_(false) {
   SetLayoutManager(new views::FillLayout);
   AddChildView(container_);
 
   button_->SetProminent(true);
   button_->SetBgColorOverride(gfx::kGoogleRed700);
-  button_->AdjustFontSize(kTrayTextFontSizeIncrease);
 
   container_->AddChildView(button_);
   Shell::Get()->system_tray_notifier()->AddLogoutButtonObserver(this);
   SetVisible(false);
 }
 
 LogoutButtonTray::~LogoutButtonTray() {
   Shell::Get()->system_tray_notifier()->RemoveLogoutButtonObserver(this);
 }
 
@@ skipping 54 matching lines @@
     button_->SetText(base::string16());
     button_->SetAccessibleName(title);
     button_->SetImage(views::Button::STATE_NORMAL,
                       gfx::CreateVectorIcon(kShelfLogoutIcon, kTrayIconColor));
     button_->SetMinSize(gfx::Size(kTrayItemSize, kTrayItemSize));
   }
   UpdateVisibility();
 }
 
 }  // namespace ash