Introduce a type of View background that stays in sync with its host

ash/system/audio/volume_view.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/audio/volume_view.h"
 
 #include <algorithm>
 
 #include "ash/metrics/user_metrics_action.h"
 #include "ash/resources/vector_icons/vector_icons.h"
 #include "ash/shell_port.h"
 #include "ash/strings/grit/ash_strings.h"
 #include "ash/system/tray/actionable_view.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_popup_utils.h"
 #include "ash/system/tray/tri_view.h"
 #include "chromeos/audio/cras_audio_handler.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/paint_vector_icon.h"
 #include "ui/gfx/vector_icon_types.h"
+#include "ui/native_theme/native_theme.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/slider.h"
 #include "ui/views/layout/fill_layout.h"
 
 using chromeos::CrasAudioHandler;
 
 namespace ash {
@@ skipping 90 matching lines @@
 
   icon_ = new VolumeButton(owner, this);
   tri_view_->AddView(TriView::Container::START, icon_);
 
   slider_ = TrayPopupUtils::CreateSlider(this);
   slider_->SetValue(CrasAudioHandler::Get()->GetOutputVolumePercent() / 100.0f);
   slider_->SetAccessibleName(
       l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_VOLUME));
   tri_view_->AddView(TriView::Container::CENTER, slider_);
 
-  set_background(views::Background::CreateSolidBackground(kBackgroundColor));
+  set_background(views::Background::CreateThemedSolidBackground(
+      this, ui::NativeTheme::kColorId_BubbleBackground));
+
   Update();
 }
 
 VolumeView::~VolumeView() {}
 
 void VolumeView::Update() {
   icon_->Update();
   slider_->UpdateState(!CrasAudioHandler::Get()->IsOutputMuted());
   UpdateDeviceTypeAndMore();
   Layout();
@@ skipping 127 matching lines @@
     if (new_volume > current_volume)
       HandleVolumeUp(new_volume);
     else
       HandleVolumeDown(new_volume);
   }
   icon_->Update();
 }
 
 }  // namespace tray
 }  // namespace ash