fix: Set background for WCO container (#35610)

* fix: Set background for WCO container

* Add background when invalidating as well

Co-authored-by: Raymond Zhao <[email protected]>

shell/browser/ui/views/win_caption_button_container.cc

@@ -14,6 +14,7 @@
 #include "shell/browser/ui/views/win_frame_view.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/strings/grit/ui_strings.h"
+#include "ui/views/background.h"
 #include "ui/views/layout/flex_layout.h"
 #include "ui/views/view_class_properties.h"
 
@@ -128,6 +129,8 @@ void WinCaptionButtonContainer::AddedToWidget() {
   UpdateButtons();
 
   if (frame_view_->window()->IsWindowControlsOverlayEnabled()) {
+    SetBackground(views::CreateSolidBackground(
+        frame_view_->window()->overlay_button_color()));
     SetPaintToLayer();
   }
 }

shell/browser/ui/views/win_frame_view.cc

@@ -19,6 +19,7 @@
 #include "ui/display/win/dpi.h"
 #include "ui/display/win/screen_win.h"
 #include "ui/gfx/geometry/dip_util.h"
+#include "ui/views/background.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/win/hwnd_util.h"
 
@@ -58,6 +59,8 @@ void WinFrameView::InvalidateCaptionButtons() {
   if (!caption_button_container_)
     return;
 
+  caption_button_container_->SetBackground(
+      views::CreateSolidBackground(window()->overlay_button_color()));
   caption_button_container_->InvalidateLayout();
   caption_button_container_->SchedulePaint();
 }