Replace layer id with Element id for tracking scrollbar animation controllers

cc/layers/painted_scrollbar_layer.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/painted_scrollbar_layer.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "cc/base/math_util.h"
@@ skipping 16 matching lines @@
 
 std::unique_ptr<LayerImpl> PaintedScrollbarLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return PaintedScrollbarLayerImpl::Create(
       tree_impl, id(), scrollbar_->Orientation(),
       scrollbar_->IsLeftSideVerticalScrollbar(), scrollbar_->IsOverlay());
 }
 
 scoped_refptr<PaintedScrollbarLayer> PaintedScrollbarLayer::Create(
     std::unique_ptr<Scrollbar> scrollbar,
-    int scroll_layer_id) {
-  return make_scoped_refptr(
-      new PaintedScrollbarLayer(std::move(scrollbar), scroll_layer_id));
+    int scroll_layer_id,
+    ElementId scroll_element_id) {
+  return make_scoped_refptr(new PaintedScrollbarLayer(
+      std::move(scrollbar), scroll_layer_id, scroll_element_id));
 }
 
 PaintedScrollbarLayer::PaintedScrollbarLayer(
     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),
       internal_contents_scale_(1.f),
       thumb_thickness_(scrollbar_->ThumbThickness()),
       thumb_length_(scrollbar_->ThumbLength()),
       is_overlay_(scrollbar_->IsOverlay()),
       has_thumb_(scrollbar_->HasThumb()),
       thumb_opacity_(scrollbar_->ThumbOpacity()) {
   if (!scrollbar_->IsOverlay())
     AddMainThreadScrollingReasons(
         MainThreadScrollingReason::kScrollbarScrolling);
 }
 
 PaintedScrollbarLayer::~PaintedScrollbarLayer() {}
 
-int PaintedScrollbarLayer::ScrollLayerId() const {
-  return scroll_layer_id_;
+ElementId PaintedScrollbarLayer::scroll_element_id() const {
+  return scroll_element_id_;
 }
 
-void PaintedScrollbarLayer::SetScrollLayer(int layer_id) {
-  if (layer_id == scroll_layer_id_)
+void PaintedScrollbarLayer::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 PaintedScrollbarLayer::OpacityCanAnimateOnImplThread() const {
   return scrollbar_->IsOverlay();
 }
 
 bool PaintedScrollbarLayer::AlwaysUseActiveTreeOpacity() const {
   return true;
 }
 
 ScrollbarOrientation PaintedScrollbarLayer::orientation() const {
   return scrollbar_->Orientation();
 }
 
 void PaintedScrollbarLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
 
   PaintedScrollbarLayerImpl* scrollbar_layer =
       static_cast<PaintedScrollbarLayerImpl*>(layer);
 
-  scrollbar_layer->SetScrollLayerId(scroll_layer_id_);
+  scrollbar_layer->SetScrollInfo(scroll_layer_id_, scroll_element_id_);
   scrollbar_layer->set_internal_contents_scale_and_bounds(
       internal_contents_scale_, internal_content_bounds_);
 
   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 {
@@ skipping 184 matching lines @@
 
   scrollbar_->PaintPart(&canvas, part, layer_rect);
   // Make sure that the pixels are no longer mutable to unavoid unnecessary
   // allocation and copying.
   skbitmap.setImmutable();
 
   return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc