Replace layer id with Element id for tracking scrollbar animation controllers

cc/layers/painted_overlay_scrollbar_layer.cc

 // 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.
 
 #include "cc/layers/painted_overlay_scrollbar_layer.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "cc/base/math_util.h"
@@ skipping 14 matching lines @@
 
 std::unique_ptr<LayerImpl> PaintedOverlayScrollbarLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return PaintedOverlayScrollbarLayerImpl::Create(
       tree_impl, id(), scrollbar_->Orientation(),
       scrollbar_->IsLeftSideVerticalScrollbar());
 }
 
 scoped_refptr<PaintedOverlayScrollbarLayer>
 PaintedOverlayScrollbarLayer::Create(std::unique_ptr<Scrollbar> scrollbar,
-                                     int scroll_layer_id) {
-  return make_scoped_refptr(
-      new PaintedOverlayScrollbarLayer(std::move(scrollbar), scroll_layer_id));
+                                     int scroll_layer_id,
+                                     ElementId scroll_element_id) {
+  return make_scoped_refptr(new PaintedOverlayScrollbarLayer(
+      std::move(scrollbar), scroll_layer_id, scroll_element_id));
 }
 
 PaintedOverlayScrollbarLayer::PaintedOverlayScrollbarLayer(
     std::unique_ptr<Scrollbar> scrollbar,
-    int scroll_layer_id)
+    int scroll_layer_id,
+    ElementId scroll_element_id)
     : scrollbar_(std::move(scrollbar)),
       scroll_layer_id_(scroll_layer_id),
+      scroll_element_id_(scroll_element_id),
       thumb_thickness_(scrollbar_->ThumbThickness()),
       thumb_length_(scrollbar_->ThumbLength()) {
   DCHECK(scrollbar_->UsesNinePatchThumbResource());
 }
 
 PaintedOverlayScrollbarLayer::~PaintedOverlayScrollbarLayer() {}
 
 int PaintedOverlayScrollbarLayer::ScrollLayerId() const {
   return scroll_layer_id_;
 }
 
-void PaintedOverlayScrollbarLayer::SetScrollLayer(int layer_id) {
-  if (layer_id == scroll_layer_id_)
+ElementId PaintedOverlayScrollbarLayer::ScrollElementId() const {
+  return scroll_element_id_;
+}
+
+void PaintedOverlayScrollbarLayer::SetScrollInfo(int layer_id,
+                                                 ElementId element_id) {
+  if (layer_id == scroll_layer_id_ && element_id == scroll_element_id_)
     return;
 
   scroll_layer_id_ = layer_id;
+  scroll_element_id_ = element_id;
   SetNeedsFullTreeSync();
 }
 
 bool PaintedOverlayScrollbarLayer::OpacityCanAnimateOnImplThread() const {
   return scrollbar_->IsOverlay();
 }
 
 bool PaintedOverlayScrollbarLayer::AlwaysUseActiveTreeOpacity() const {
   return true;
 }
 
 ScrollbarOrientation PaintedOverlayScrollbarLayer::orientation() const {
   return scrollbar_->Orientation();
 }
 
 void PaintedOverlayScrollbarLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
 
   PaintedOverlayScrollbarLayerImpl* scrollbar_layer =
       static_cast<PaintedOverlayScrollbarLayerImpl*>(layer);
 
-  scrollbar_layer->SetScrollLayerId(scroll_layer_id_);
+  scrollbar_layer->SetScrollInfo(scroll_layer_id_, scroll_element_id_);
 
   scrollbar_layer->SetThumbThickness(thumb_thickness_);
   scrollbar_layer->SetThumbLength(thumb_length_);
   if (orientation() == HORIZONTAL) {
     scrollbar_layer->SetTrackStart(track_rect_.x() - location_.x());
     scrollbar_layer->SetTrackLength(track_rect_.width());
   } else {
     scrollbar_layer->SetTrackStart(track_rect_.y() - location_.y());
     scrollbar_layer->SetTrackLength(track_rect_.height());
   }
@@ skipping 72 matching lines @@
 
   thumb_resource_ = ScopedUIResource::Create(
       layer_tree_host()->GetUIResourceManager(), UIResourceBitmap(skbitmap));
 
   SetNeedsPushProperties();
 
   return true;
 }
 
 }  // namespace cc