Implement CSS: scroll-boundary-behavior

cc/layers/layer.cc

 // Copyright 2010 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.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 47 matching lines @@
       user_scrollable_horizontal(true),
       user_scrollable_vertical(true),
       main_thread_scrolling_reasons(
           MainThreadScrollingReason::kNotScrollingOnMain),
       is_container_for_fixed_position_layers(false),
       mutable_properties(MutableProperty::kNone),
       scroll_parent(nullptr),
       clip_parent(nullptr),
       has_will_change_transform_hint(false),
       hide_layer_and_subtree(false),
-      client(nullptr) {}
+      client(nullptr),
+      scroll_boundary_behavior(
+          ScrollBoundaryBehavior::kScrollBoundaryBehaviorTypeAuto) {}
 
 Layer::Inputs::~Inputs() {}
 
 scoped_refptr<Layer> Layer::Create() {
   return make_scoped_refptr(new Layer());
 }
 
 Layer::Layer()
     : ignore_set_needs_commit_(false),
       parent_(nullptr),
@@ skipping 220 matching lines @@
     auto& scroll_tree = layer_tree_host_->property_trees()->scroll_tree;
     if (auto* scroll_node = scroll_tree.Node(scroll_tree_index_))
       scroll_node->bounds = inputs_.bounds;
     else
       SetPropertyTreesNeedRebuild();
   }
 
   SetNeedsCommit();
 }
 
+void Layer::SetScrollBoundaryBehavior(const ScrollBoundaryBehavior& behavior) {
+  DCHECK(IsPropertyChangeAllowed());
+  if (scroll_boundary_behavior() == behavior)
+    return;
+  inputs_.scroll_boundary_behavior = behavior;
+  if (!layer_tree_host_)
+    return;
+
+  if (scrollable()) {
+    auto& scroll_tree = layer_tree_host_->property_trees()->scroll_tree;
+    if (auto* scroll_node = scroll_tree.Node(scroll_tree_index_))
+      scroll_node->scroll_boundary_behavior = behavior;
+    else
+      SetPropertyTreesNeedRebuild();
+  }
+
+  SetNeedsCommit();
+}
+
 Layer* Layer::RootLayer() {
   Layer* layer = this;
   while (layer->parent())
     layer = layer->parent();
   return layer;
 }
 
 void Layer::RemoveAllChildren() {
   DCHECK(IsPropertyChangeAllowed());
   while (inputs_.children.size()) {
@@ skipping 1107 matching lines @@
       ->subtree_has_copy_request;
 }
 
 gfx::Transform Layer::ScreenSpaceTransform() const {
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc