Extract the view of control buttons on notification into a separated class

ui/arc/notification/arc_notification_content_view_unittest.cc

 // Copyright 2017 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 <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <utility>
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/arc/notification/arc_notification_content_view.h"
 #include "ui/arc/notification/arc_notification_delegate.h"
 #include "ui/arc/notification/arc_notification_item.h"
 #include "ui/arc/notification/arc_notification_surface.h"
 #include "ui/arc/notification/arc_notification_view.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/views/message_center_controller.h"
 #include "ui/message_center/views/message_view_factory.h"
-#include "ui/views/controls/button/image_button.h"
+#include "ui/message_center/views/notification_control_buttons_view.h"
+#include "ui/message_center/views/padded_button.h"
 #include "ui/views/test/views_test_base.h"
 
 namespace arc {
 
 namespace {
 
 constexpr char kNotificationIdPrefix[] = "ARC_NOTIFICATION_";
 
 class MockNotificationSurface : public ArcNotificationSurface {
  public:
@@ skipping 201 matching lines @@
     EXPECT_FALSE(wrapper_widget_);
     EXPECT_FALSE(notification_view_);
 
     surface_manager_.reset();
 
     views::ViewsTestBase::TearDown();
   }
 
   void PressCloseButton() {
     DummyEvent dummy_event;
-    views::ImageButton* close_button =
-        GetArcNotificationContentView()->close_button_.get();
+    auto* control_buttons_view =
+        GetArcNotificationContentView()->control_buttons_view_;
+    message_center::PaddedButton* close_button =
+        control_buttons_view->close_button_for_testing();
     ASSERT_NE(nullptr, close_button);
-    GetArcNotificationContentView()->ButtonPressed(close_button, dummy_event);
+    control_buttons_view->ButtonPressed(close_button, dummy_event);
   }
 
   void CreateAndShowNotificationView(
       const message_center::Notification& notification) {
     DCHECK(!notification_view_);
 
     notification_view_.reset(static_cast<ArcNotificationView*>(
         message_center::MessageViewFactory::Create(controller(), notification,
                                                    true)));
     notification_view_->set_owned_by_client();
@@ skipping 104 matching lines @@
 
   EXPECT_EQ(1u, surface_manager()->surface_found_count());
   EXPECT_FALSE(controller()->IsRemoved(notification_item->GetNotificationId()));
   PressCloseButton();
   EXPECT_TRUE(controller()->IsRemoved(notification_item->GetNotificationId()));
 
   CloseNotificationView();
 }
 
 }  // namespace arc