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 236 matching lines @@
 
   if (layer_property_changed_) {
     layer->layer_tree_impl()->set_needs_update_draw_properties();
     layer->layer_property_changed_ = true;
   }
 
   layer->SetBounds(bounds_);
   if (scrollable_)
     layer->SetScrollable(scroll_container_bounds_);
   layer->SetMutableProperties(mutable_properties_);
+  layer->SetScrollBoundaryBehavior(scroll_boundary_behavior_);
 
   // If the main thread commits multiple times before the impl thread actually
   // draws, then damage tracking will become incorrect if we simply clobber the
   // update_rect here. The LayerImpl's update_rect needs to accumulate (i.e.
   // union) any update changes that have occurred on the main thread.
   update_rect_.Union(layer->update_rect());
   layer->SetUpdateRect(update_rect_);
 
   if (owned_debug_info_)
     layer->SetDebugInfo(std::move(owned_debug_info_));
@@ skipping 406 matching lines @@
 
 gfx::Vector2dF LayerImpl::ClampScrollToMaxScrollOffset() {
   gfx::ScrollOffset old_offset = CurrentScrollOffset();
   gfx::ScrollOffset clamped_offset = ClampScrollOffsetToLimits(old_offset);
   gfx::Vector2dF delta = clamped_offset.DeltaFrom(old_offset);
   if (!delta.IsZero())
     ScrollBy(delta);
   return delta;
 }
 
+void LayerImpl::SetScrollBoundaryBehavior(
+    const ScrollBoundaryBehavior& behavior) {
+  if (scroll_boundary_behavior_ == behavior)
+    return;
+  scroll_boundary_behavior_ = behavior;
+  NoteLayerPropertyChanged();
+}
+
 void LayerImpl::SetNeedsPushProperties() {
   // There's no need to push layer properties on the active tree.
   if (!needs_push_properties_ && !layer_tree_impl()->IsActiveTree()) {
     needs_push_properties_ = true;
     layer_tree_impl()->AddLayerShouldPushProperties(this);
   }
 }
 
 void LayerImpl::GetAllPrioritizedTilesForTracing(
     std::vector<PrioritizedTile>* prioritized_tiles) const {
@@ skipping 219 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