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

ui/views/bubble/tray_bubble_view.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 "ui/views/bubble/tray_bubble_view.h"
 
 #include <algorithm>
 
 #include "base/macros.h"
 #include "cc/paint/paint_flags.h"
@@ skipping 157 matching lines @@
 using internal::BottomAlignedBoxLayout;
 
 TrayBubbleView::InitParams::InitParams(AnchorAlignment anchor_alignment,
                                        int min_width,
                                        int max_width)
     : anchor_alignment(anchor_alignment),
       min_width(min_width),
       max_width(max_width),
       max_height(0),
       can_activate(false),
-      close_on_deactivate(true),
-      bg_color(gfx::kPlaceholderColor) {}
+      close_on_deactivate(true) {}
 
 TrayBubbleView::InitParams::InitParams(const InitParams& other) = default;
 
 // static
 TrayBubbleView* TrayBubbleView::Create(View* anchor,
                                        Delegate* delegate,
                                        InitParams* init_params) {
   return new TrayBubbleView(anchor, delegate, *init_params);
 }
 
 TrayBubbleView::TrayBubbleView(View* anchor,
                                Delegate* delegate,
                                const InitParams& init_params)
     : BubbleDialogDelegateView(anchor,
                                GetArrowAlignment(init_params.anchor_alignment)),
       params_(init_params),
       layout_(new BottomAlignedBoxLayout(this)),
       delegate_(delegate),
       preferred_width_(init_params.min_width),
-      bubble_border_(new BubbleBorder(arrow(),
-                                      BubbleBorder::NO_ASSETS,
-                                      init_params.bg_color)),
+      bubble_border_(new BubbleBorder(
+          arrow(),
+          BubbleBorder::NO_ASSETS,
+          init_params.bg_color.value_or(gfx::kPlaceholderColor))),
       owned_bubble_border_(bubble_border_),
       is_gesture_dragging_(false),
       mouse_actively_entered_(false) {
+  bubble_border_->set_use_theme_background_color(!init_params.bg_color);
   bubble_border_->set_alignment(BubbleBorder::ALIGN_EDGE_TO_ANCHOR_EDGE);
   bubble_border_->set_paint_arrow(BubbleBorder::PAINT_NONE);
   set_can_activate(params_.can_activate);
   DCHECK(anchor_widget());  // Computed by BubbleDialogDelegateView().
   set_notify_enter_exit_on_child(true);
   set_close_on_deactivate(init_params.close_on_deactivate);
   set_margins(gfx::Insets());
   SetPaintToLayer();
 
   bubble_content_mask_.reset(
@@ skipping 162 matching lines @@
 
 void TrayBubbleView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (details.is_add && details.child == this) {
     details.parent->SetPaintToLayer();
     details.parent->layer()->SetMasksToBounds(true);
   }
 }
 
 }  // namespace views