Make message center always scroll up upon notification removal

ui/message_center/views/message_center_view.cc

 // Copyright (c) 2013 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 "ui/message_center/views/message_center_view.h"
 
 #include <list>
 #include <map>
 
+#include "base/command_line.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "grit/ui_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/animation/multi_animation.h"
 #include "ui/gfx/animation/slide_animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/insets.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/message_center_style.h"
+#include "ui/message_center/message_center_switches.h"
 #include "ui/message_center/message_center_tray.h"
 #include "ui/message_center/message_center_types.h"
 #include "ui/message_center/views/message_center_button_bar.h"
 #include "ui/message_center/views/message_view.h"
 #include "ui/message_center/views/message_view_context_menu_controller.h"
 #include "ui/message_center/views/notification_view.h"
 #include "ui/message_center/views/notifier_settings_view.h"
 #include "ui/resources/grit/ui_resources.h"
 #include "ui/views/animation/bounds_animator.h"
 #include "ui/views/animation/bounds_animator_observer.h"
@@ skipping 378 matching lines @@
   if (!animator_.get()) {
     animator_.reset(new views::BoundsAnimator(this));
     animator_->AddObserver(this);
   }
 
   if (!clearing_all_views_.empty()) {
     AnimateClearingOneNotification();
     return;
   }
 
-  if (top_down_)
+  if (top_down_ ||
+      CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableMessageCenterAlwaysScrollUpUponNotificationRemoval))
     AnimateNotificationsBelowTarget();
   else
     AnimateNotificationsAboveTarget();
 
   adding_views_.clear();
   deleting_views_.clear();
 }
 
 void MessageListView::AnimateNotificationsBelowTarget() {
   int last_index = -1;
@@ skipping 565 matching lines @@
   scroller_->InvalidateLayout();
   PreferredSizeChanged();
   Layout();
 }
 
 void MessageCenterView::SetNotificationViewForTest(MessageView* view) {
   message_list_view_->AddNotificationAt(view, 0);
 }
 
 }  // namespace message_center