Make all scrollable layers visible to hit testing.

cc/trees/scroll_node.h

 // 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.
 
 #ifndef CC_TREES_SCROLL_NODE_H_
 #define CC_TREES_SCROLL_NODE_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/output/filter_operations.h"
 #include "ui/gfx/geometry/size.h"
@@ skipping 43 matching lines @@
 
   // This offset is used when |scrollable| is false and there isn't a transform
   // node already present that covers this offset.
   gfx::Vector2dF offset_to_transform_parent;
 
   bool should_flatten;
   bool user_scrollable_horizontal;
   bool user_scrollable_vertical;
   ElementId element_id;
   int transform_id;
-  // Number of drawn layers pointing to this node or any of its descendants.
-  int num_drawn_descendants;
 
   bool operator==(const ScrollNode& other) const;
 
   void ToProtobuf(proto::TreeNode* proto) const;
   void FromProtobuf(const proto::TreeNode& proto);
   void AsValueInto(base::trace_event::TracedValue* value) const;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_SCROLL_NODE_H_