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

ash/system/tray/tray_details_view.cc

Index: ash/system/tray/tray_details_view.cc
diff --git a/ash/system/tray/tray_details_view.cc b/ash/system/tray/tray_details_view.cc
index 9ae56da2b127dd9202d3bba004b5729f7b482598..89455d514e5602fa36440133c45e0a5747072372 100644
--- a/ash/system/tray/tray_details_view.cc
+++ b/ash/system/tray/tray_details_view.cc
@@ -238,7 +238,8 @@ TrayDetailsView::TrayDetailsView(SystemTrayItem* owner)
       tri_view_(nullptr),
       back_button_(nullptr) {
   SetLayoutManager(box_layout_);
-  set_background(views::Background::CreateSolidBackground(kBackgroundColor));
+  set_background(views::Background::CreateThemedSolidBackground(
+      this, ui::NativeTheme::kColorId_BubbleBackground));
 }
 
 TrayDetailsView::~TrayDetailsView() {}
@@ -295,8 +296,8 @@ void TrayDetailsView::CreateScrollableList() {
   // Make the |scroller_| have a layer to clip |scroll_content_|'s children.
   // TODO(varkha): Make the sticky rows work with EnableViewPortLayer().
   scroller_->SetPaintToLayer();
-  scroller_->set_background(
-      views::Background::CreateSolidBackground(kBackgroundColor));
+  scroller_->set_background(views::Background::CreateThemedSolidBackground(
+      scroller_, ui::NativeTheme::kColorId_BubbleBackground));
   scroller_->layer()->SetMasksToBounds(true);
 
   AddChildView(scroller_);