Extract sidebar, lifecycle shell, and canvas unmerged draw

src/legacy_canvas_draw_merge_services.h

@@ -945,6 +945,49 @@ inline void execute_legacy_canvas_draw_merge_background_setup(
     }
 }
 
+template <
+    typename PrepareBlendCache,
+    typename DrawBackground,
+    typename ConfigureBlendState,
+    typename DisableDepthTest,
+    typename PlanOnionRange,
+    typename ShouldDrawPlane,
+    typename VisitLayerPlane,
+    typename LogOnionRangeFailure,
+    typename CompositeBlendCache>
+inline void execute_legacy_canvas_draw_unmerged_shell(
+    bool use_blend,
+    size_t layer_count,
+    PrepareBlendCache&& prepare_blend_cache,
+    DrawBackground&& draw_background,
+    ConfigureBlendState&& configure_blend_state,
+    DisableDepthTest&& disable_depth_test,
+    PlanOnionRange&& plan_onion_range,
+    ShouldDrawPlane&& should_draw_plane,
+    VisitLayerPlane&& visit_layer_plane,
+    LogOnionRangeFailure&& log_onion_range_failure,
+    CompositeBlendCache&& composite_blend_cache)
+{
+    if (use_blend) {
+        prepare_blend_cache();
+    }
+
+    draw_background();
+    configure_blend_state(use_blend);
+    disable_depth_test();
+
+    execute_legacy_canvas_draw_layer_traversal(
+        layer_count,
+        std::forward<PlanOnionRange>(plan_onion_range),
+        std::forward<ShouldDrawPlane>(should_draw_plane),
+        std::forward<VisitLayerPlane>(visit_layer_plane),
+        std::forward<LogOnionRangeFailure>(log_onion_range_failure));
+
+    if (use_blend) {
+        composite_blend_cache();
+    }
+}
+
 inline void execute_legacy_canvas_draw_merge_plane_setup(
     const LegacyCanvasDrawMergePlaneSetupUniforms& uniforms,
     const LegacyCanvasDrawMergePlaneSetupExecution& execution)