Make all scrollable layers visible to hit testing.

cc/trees/scroll_node.cc

 // Copyright 2016 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 "base/trace_event/trace_event_argument.h"
 #include "cc/animation/element_id.h"
 #include "cc/base/math_util.h"
 #include "cc/input/main_thread_scrolling_reason.h"
 #include "cc/proto/gfx_conversions.h"
 #include "cc/trees/scroll_node.h"
 
 namespace cc {
 
 ScrollNode::ScrollNode()
     : id(-1),
       parent_id(-1),
       owner_id(-1),
       scrollable(false),
       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),
-      transform_id(0),
-      num_drawn_descendants(0) {}
+      transform_id(0) {}
 
 ScrollNode::ScrollNode(const ScrollNode& other) = default;
 
 bool ScrollNode::operator==(const ScrollNode& other) const {
   return id == other.id && parent_id == other.parent_id &&
          owner_id == other.owner_id && 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 &&
@@ skipping 23 matching lines @@
                              offset_to_transform_parent, value);
   value->SetBoolean("should_flatten", should_flatten);
   value->SetBoolean("user_scrollable_horizontal", user_scrollable_horizontal);
   value->SetBoolean("user_scrollable_vertical", user_scrollable_vertical);
 
   element_id.AddToTracedValue(value);
   value->SetInteger("transform_id", transform_id);
 }
 
 }  // namespace cc