Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

ash/common/system/status_area_widget.cc

 // Copyright (c) 2012 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/status_area_widget.h"
 
 #include "ash/common/shelf/wm_shelf.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/system/overview/overview_button_tray.h"
 #include "ash/common/system/status_area_widget_delegate.h"
@@ skipping 136 matching lines @@
 void StatusAreaWidget::OnMouseEvent(ui::MouseEvent* event) {
   Widget::OnMouseEvent(event);
   wm_shelf_->UpdateAutoHideForMouseEvent(event);
 }
 
 void StatusAreaWidget::OnGestureEvent(ui::GestureEvent* event) {
   Widget::OnGestureEvent(event);
   wm_shelf_->UpdateAutoHideForGestureEvent(event);
 }
 
+void StatusAreaWidget::UpdateShelfItemBackground(int alpha) {
+  web_notification_tray_->UpdateShelfItemBackground(alpha);
+  system_tray_->UpdateShelfItemBackground(alpha);
+#if defined(OS_CHROMEOS)
+  virtual_keyboard_tray_->UpdateShelfItemBackground(alpha);
+  logout_button_tray_->UpdateShelfItemBackground(alpha);
+  ime_menu_tray_->UpdateShelfItemBackground(alpha);
+  palette_tray_->UpdateShelfItemBackground(alpha);
+#endif
+  overview_button_tray_->UpdateShelfItemBackground(alpha);
+}
+
 void StatusAreaWidget::AddSystemTray() {
   system_tray_ = new SystemTray(wm_shelf_);
   status_area_widget_delegate_->AddTray(system_tray_);
 }
 
 void StatusAreaWidget::AddWebNotificationTray() {
   DCHECK(system_tray_);
   web_notification_tray_ = new WebNotificationTray(
       wm_shelf_, WmLookup::Get()->GetWindowForWidget(this), system_tray_);
   status_area_widget_delegate_->AddTray(web_notification_tray_);
@@ skipping 57 matching lines @@
     web_notification_tray_->UpdateAfterLoginStatusChange(login_status);
 #if defined(OS_CHROMEOS)
   if (logout_button_tray_)
     logout_button_tray_->UpdateAfterLoginStatusChange(login_status);
 #endif
   if (overview_button_tray_)
     overview_button_tray_->UpdateAfterLoginStatusChange(login_status);
 }
 
 }  // namespace ash