Add a test for nested display list rtree

Author: iskakaushik

display_list/display_list_unittests.cc

@@ -1650,6 +1650,26 @@ TEST(DisplayList, RTreeOfSaveLayerFilterScene) {
   test_rtree(rtree, {19, 19, 51, 51}, rects, {0, 1});
 }
 
+TEST(DisplayList, NestedDisplayListRTreesAreSparse) {
+  DisplayListBuilder nested_dl_builder;
+  nested_dl_builder.drawRect({10, 10, 20, 20});
+  nested_dl_builder.drawRect({50, 50, 60, 60});
+  auto nested_display_list = nested_dl_builder.Build();
+
+  DisplayListBuilder builder;
+  builder.drawDisplayList(nested_display_list);
+  auto display_list = builder.Build();
+
+  auto rtree = display_list->rtree();
+  std::vector<SkRect> rects = {
+      {10, 10, 20, 20},
+      {50, 50, 60, 60},
+  };
+
+  // Hitting both sub-dl drawRect calls
+  test_rtree(rtree, {19, 19, 51, 51}, rects, {0, 1});
+}
+
 TEST(DisplayList, RemoveUnnecessarySaveRestorePairs) {
   {
     DisplayListBuilder builder;

display_list/display_list_utils.cc

@@ -682,7 +682,7 @@ void DisplayListBoundsCalculator::drawDisplayList(
           display_list->rtree()->searchNonOverlappingDrawnRects(bounds);
       for (const SkRect& rect : rects) {
         // TODO (https://github.com/flutter/flutter/issues/114919): Attributes
-        // are not neccessarily `kDrawDisplayListFlags`.
+        // are not necessarily `kDrawDisplayListFlags`.
         AccumulateOpBounds(rect, kDrawDisplayListFlags);
       }
       return;