cc: Construct the RSLL without using layer hierarchy

cc/trees/property_tree.cc

 // Copyright 2014 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 <stddef.h>
 
 #include <set>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 510 matching lines @@
       main_thread_scrolling_reasons(
           MainThreadScrollingReason::kNotScrollingOnMain),
       contains_non_fast_scrollable_region(false),
       max_scroll_offset_affected_by_page_scale(false),
       is_inner_viewport_scroll_layer(false),
       is_outer_viewport_scroll_layer(false),
       should_flatten(false),
       user_scrollable_horizontal(false),
       user_scrollable_vertical(false),
       element_id(0),
-      transform_id(0) {}
+      transform_id(0),
+      num_drawn_descendants(0) {}
 
 ScrollNodeData::ScrollNodeData(const ScrollNodeData& other) = default;
 
 bool ScrollNodeData::operator==(const ScrollNodeData& other) const {
   return scrollable == other.scrollable &&
          main_thread_scrolling_reasons == other.main_thread_scrolling_reasons &&
          contains_non_fast_scrollable_region ==
              other.contains_non_fast_scrollable_region &&
          scroll_clip_layer_bounds == other.scroll_clip_layer_bounds &&
          bounds == other.bounds &&
@@ skipping 1399 matching lines @@
       break;
     case ALL_TREES:
       transform_tree.ResetChangeTracking();
       effect_tree.ResetChangeTracking();
   }
   changed = false;
   full_tree_damaged = false;
 }
 
 }  // namespace cc