Remove scroll layer ids from scrollbar layers

cc/layers/scrollbar_layer_impl_base.cc

 // Copyright 2013 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/scrollbar_layer_impl_base.h"
 
 #include <algorithm>
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace cc {
 
 ScrollbarLayerImplBase::ScrollbarLayerImplBase(
     LayerTreeImpl* tree_impl,
     int id,
     ScrollbarOrientation orientation,
     bool is_left_side_vertical_scrollbar,
     bool is_overlay)
     : LayerImpl(tree_impl, id),
-      scroll_layer_id_(Layer::INVALID_ID),
       is_overlay_scrollbar_(is_overlay),
       thumb_thickness_scale_factor_(1.f),
       current_pos_(0.f),
       clip_layer_length_(0.f),
       scroll_layer_length_(0.f),
       orientation_(orientation),
       is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar),
       vertical_adjust_(0.f) {}
 
 ScrollbarLayerImplBase::~ScrollbarLayerImplBase() {
   layer_tree_impl()->UnregisterScrollbar(this);
 }
 
 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
   LayerImpl::PushPropertiesTo(layer);
   DCHECK(layer->ToScrollbarLayer());
   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
-  layer->ToScrollbarLayer()->SetScrollInfo(ScrollLayerId(),
-                                           scroll_element_id());
+  layer->ToScrollbarLayer()->SetScrollElementId(scroll_element_id());
 }
 
 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
   return this;
 }
 
-void ScrollbarLayerImplBase::SetScrollInfo(int scroll_layer_id,
-                                           ElementId scroll_element_id) {
-  if (scroll_layer_id_ == scroll_layer_id &&
-      scroll_element_id == scroll_element_id)
+void ScrollbarLayerImplBase::SetScrollElementId(ElementId scroll_element_id) {
+  if (scroll_element_id_ == scroll_element_id)

[wkorman, 2017/04/20 17:53:47]

Can we add a unit test that would have caught this?

     return;
 
   layer_tree_impl()->UnregisterScrollbar(this);
-
-  scroll_layer_id_ = scroll_layer_id;
   scroll_element_id_ = scroll_element_id;
-
   layer_tree_impl()->RegisterScrollbar(this);
 }
 
 bool ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
   if (current_pos_ == current_pos)
     return false;
   current_pos_ = current_pos;
   NoteLayerPropertyChanged();
   return true;
 }
 
 bool ScrollbarLayerImplBase::CanScrollOrientation() const {
-  LayerImpl* scroll_layer = layer_tree_impl()->LayerById(scroll_layer_id_);
+  // TODO(pdr): Refactor this to not depend on layers by using the associated
+  // scroll node's user_scrollable values.
+  LayerImpl* scroll_layer =
+      layer_tree_impl()->LayerByElementId(scroll_element_id_);
   if (!scroll_layer)
     return false;
   return scroll_layer->user_scrollable(orientation()) &&
          clip_layer_length_ < scroll_layer_length_;
 }
 
 bool ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
   if (vertical_adjust_ == vertical_adjust)
     return false;
   vertical_adjust_ = vertical_adjust;
@@ skipping 149 matching lines @@
   layer_tree_impl()->AddToOpacityAnimationsMap(id(), opacity);
 
   node->opacity = opacity;
   node->effect_changed = true;
   property_trees->changed = true;
   property_trees->effect_tree.set_needs_update(true);
   layer_tree_impl()->set_needs_update_draw_properties();
 }
 
 }  // namespace cc