Reduce views::Border creation verbosity by promoting factory functions

ash/common/system/chromeos/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/common/system/chromeos/session/logout_button_tray.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/common/material_design/material_design_controller.h"
@@ skipping 102 matching lines @@
     // Base font size + 2 = 14.
     // TODO(estade): should this 2 be shared with other tray views? See
     // crbug.com/623987
     button->AdjustFontSize(2);
     button_ = button;
   } else {
     button_ = new LogoutButton(this);
   }
   tray_container()->AddChildView(button_);
   if (!MaterialDesignController::IsShelfMaterial())
-    tray_container()->SetBorder(views::Border::NullBorder());
+    tray_container()->SetBorder(views::NullBorder());
   WmShell::Get()->system_tray_notifier()->AddLogoutButtonObserver(this);
 }
 
 LogoutButtonTray::~LogoutButtonTray() {
   WmShell::Get()->system_tray_notifier()->RemoveLogoutButtonObserver(this);
 }
 
 void LogoutButtonTray::SetShelfAlignment(ShelfAlignment alignment) {
   // We must first update the button so that
   // TrayBackgroundView::SetShelfAlignment() can lay it out correctly.
   UpdateButtonTextAndImage(login_status_, alignment);
   TrayBackgroundView::SetShelfAlignment(alignment);
   if (!MaterialDesignController::IsShelfMaterial())
-    tray_container()->SetBorder(views::Border::NullBorder());
+    tray_container()->SetBorder(views::NullBorder());
 }
 
 base::string16 LogoutButtonTray::GetAccessibleNameForTray() {
   return button_->GetText();
 }
 
 void LogoutButtonTray::HideBubbleWithView(
     const views::TrayBubbleView* bubble_view) {}
 
 void LogoutButtonTray::ClickedOutsideBubble() {}
@@ skipping 50 matching lines @@
     button_->SetAccessibleName(title);
     button_->SetImage(
         views::LabelButton::STATE_NORMAL,
         gfx::CreateVectorIcon(gfx::VectorIconId::SHELF_LOGOUT, kTrayIconColor));
     button_->SetMinSize(gfx::Size(button_size, button_size));
   }
   UpdateVisibility();
 }
 
 }  // namespace ash