Gtk3: Render a GtkHeaderBar as the background of the tab strip

ui/views/window/custom_frame_view.cc

Index: ui/views/window/custom_frame_view.cc
diff --git a/ui/views/window/custom_frame_view.cc b/ui/views/window/custom_frame_view.cc
index bac98a4181af8df101cb57b90c406e25a584f47d..14d4630a1a49d4e93d3086f29dbcada03cb2e193 100644
--- a/ui/views/window/custom_frame_view.cc
+++ b/ui/views/window/custom_frame_view.cc
@@ -221,6 +221,14 @@ void CustomFrameView::OnPaint(gfx::Canvas* canvas) {
   if (!ShouldShowTitleBarAndBorder())
     return;
 
+  frame_background_->set_frame_color(GetFrameColor());
+  frame_background_->set_use_custom_frame(true);
+  frame_background_->set_is_active(ShouldPaintAsActive());
+  frame_background_->set_incognito(false);
+  const gfx::ImageSkia frame_image = GetFrameImage();
+  frame_background_->set_theme_image(frame_image);
+  frame_background_->set_top_area_height(frame_image.height());
+
   if (frame_->IsMaximized())
     PaintMaximizedFrameBorder(canvas);
   else
@@ -359,11 +367,6 @@ bool CustomFrameView::ShouldShowClientEdge() const {
 }
 
 void CustomFrameView::PaintRestoredFrameBorder(gfx::Canvas* canvas) {
-  frame_background_->set_frame_color(GetFrameColor());
-  const gfx::ImageSkia frame_image = GetFrameImage();
-  frame_background_->set_theme_image(frame_image);
-  frame_background_->set_top_area_height(frame_image.height());
-
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
 
   frame_background_->SetCornerImages(
@@ -381,9 +384,6 @@ void CustomFrameView::PaintRestoredFrameBorder(gfx::Canvas* canvas) {
 }
 
 void CustomFrameView::PaintMaximizedFrameBorder(gfx::Canvas* canvas) {
-  const gfx::ImageSkia frame_image = GetFrameImage();
-  frame_background_->set_theme_image(frame_image);
-  frame_background_->set_top_area_height(frame_image.height());
   frame_background_->PaintMaximized(canvas, this);
 
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();