Implement CSS: scroll-boundary-behavior

cc/layers/layer_impl.cc

 // Copyright 2012 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 "cc/layers/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 62 matching lines @@
       clip_tree_index_(ClipTree::kInvalidNodeId),
       scroll_tree_index_(ScrollTree::kInvalidNodeId),
       current_draw_mode_(DRAW_MODE_NONE),
       mutable_properties_(MutableProperty::kNone),
       debug_info_(nullptr),
       has_will_change_transform_hint_(false),
       needs_push_properties_(false),
       scrollbars_hidden_(false),
       needs_show_scrollbars_(false),
       raster_even_if_not_drawn_(false),
-      has_transform_node_(false) {
+      has_transform_node_(false),
+      scroll_boundary_behavior_(
+          ScrollBoundaryBehavior::kScrollBoundaryBehaviorTypeAuto) {
   DCHECK_GT(layer_id_, 0);
 
   DCHECK(layer_tree_impl_);
   layer_tree_impl_->RegisterLayer(this);
   layer_tree_impl_->AddToElementMap(this);
 
   SetNeedsPushProperties();
 }
 
 LayerImpl::~LayerImpl() {
@@ skipping 880 matching lines @@
 
   const bool has_valid_scroll_node =
       !!GetScrollTree().Node(scroll_tree_index());
   DCHECK(has_valid_scroll_node);
 
   return has_valid_transform_node && has_valid_effect_node &&
          has_valid_clip_node && has_valid_scroll_node;
 }
 
 }  // namespace cc