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"
@@ skipping 112 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));
 
   if (!is_default_view_) {
     tri_view_->SetContainerVisible(TriView::Container::END, false);
     Update();
     return;
   }
 
   more_button_ = new ButtonListenerActionableView(
       owner_, TrayPopupInkDropStyle::INSET_BOUNDS, this);
   TrayPopupUtils::ConfigureContainer(TriView::Container::END, more_button_);
@@ skipping 110 matching lines @@
     if (new_volume > current_volume)
       HandleVolumeUp(new_volume);
     else
       HandleVolumeDown(new_volume);
   }
   icon_->Update();
 }
 
 }  // namespace tray
 }  // namespace ash