Replace layer id with Element id for tracking scrollbar animation controllers

cc/trees/layer_tree_impl.cc

 // Copyright 2011 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/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 257 matching lines @@
   scrollbar_needs_animation |=
       (clip_layer_size_did_change || scroll_layer_size_did_change);
 
   if (y_offset_did_change && IsViewportLayerId(scroll_layer_id))
     TRACE_COUNTER_ID1("cc", "scroll_offset_y", scroll_layer->id(),
                       current_offset.y());
 
   if (scrollbar_needs_animation) {
     ScrollbarAnimationController* controller =
         layer_tree_host_impl_->ScrollbarAnimationControllerForId(
-            scroll_layer_id);
+            scroll_layer->element_id());
     if (!controller)
       return;
 
     // TODO(chaopeng) clip_layer_size_did_change should call DidResize after
     // crbug.com/701810 got fixed.
     if (scroll_layer_size_did_change) {
       controller->DidResize();
     } else {
       controller->DidScrollUpdate();
     }
@@ skipping 256 matching lines @@
   // Note: this needs to happen after SetPropertyTrees.
   target_tree->ShowScrollbars();
 }
 
 void LayerTreeImpl::ShowScrollbars() {
   LayerTreeHostCommon::CallFunctionForEveryLayer(this, [this](
                                                            LayerImpl* layer) {
     if (!layer->needs_show_scrollbars())
       return;
     ScrollbarAnimationController* controller =
-        layer_tree_host_impl_->ScrollbarAnimationControllerForId(layer->id());
+        layer_tree_host_impl_->ScrollbarAnimationControllerForId(
+            layer->element_id());
     if (controller) {
       controller->DidRequestShowFromMainThread();
       layer->set_needs_show_scrollbars(false);
     }
   });
 }
 
 void LayerTreeImpl::MoveChangeTrackingToLayers() {
   // We need to update the change tracking on property trees before we move it
   // onto the layers.
@@ skipping 163 matching lines @@
 #if DCHECK_IS_ON()
   int old_layer_id = old_node ? old_node->owning_layer_id : Layer::INVALID_ID;
   int new_layer_id = node ? node->owning_layer_id : Layer::INVALID_ID;
   DCHECK(old_layer_id == LayerIdByElementId(old_element_id));
   DCHECK(new_layer_id == LayerIdByElementId(new_element_id));
 #endif
 
   if (old_element_id == new_element_id)
     return;
 
-  // TODO(pdr): Make the scrollbar animation controller lookup based on
-  // element ids instead of layer ids.
   ScrollbarAnimationController* old_animation_controller =
-      layer_tree_host_impl_->ScrollbarAnimationControllerForId(
-          LayerIdByElementId(old_element_id));
+      layer_tree_host_impl_->ScrollbarAnimationControllerForId(old_element_id);

[wkorman, 2017/04/14 18:17:30]

Future change -- suggest renaming this method to qualify what kind of Id it is.
So, ScrollbarAnimationControllerForElementId.

[pdr., 2017/04/15 06:02:00]

+1, going to include that in this change since we both wanted it. I had done it
in a previous patch and took it out.

   ScrollbarAnimationController* new_animation_controller =
-      layer_tree_host_impl_->ScrollbarAnimationControllerForId(
-          LayerIdByElementId(new_element_id));
+      layer_tree_host_impl_->ScrollbarAnimationControllerForId(new_element_id);
 
   if (old_animation_controller)
     old_animation_controller->DidScrollEnd();
   scroll_tree.set_currently_scrolling_node(node ? node->id
                                                 : ScrollTree::kInvalidNodeId);
   if (new_animation_controller)
     new_animation_controller->DidScrollBegin();
 }
 
 void LayerTreeImpl::ClearCurrentlyScrollingNode() {
@@ skipping 963 matching lines @@
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 void LayerTreeImpl::RegisterScrollbar(ScrollbarLayerImplBase* scrollbar_layer) {
   if (scrollbar_layer->ScrollLayerId() == Layer::INVALID_ID)
     return;
 
   scrollbar_map_.insert(std::pair<int, int>(scrollbar_layer->ScrollLayerId(),
                                             scrollbar_layer->id()));
-  if (IsActiveTree() && scrollbar_layer->is_overlay_scrollbar())
+  if (IsActiveTree() && scrollbar_layer->is_overlay_scrollbar()) {
+    auto scroll_layer_id = scrollbar_layer->ScrollLayerId();
     layer_tree_host_impl_->RegisterScrollbarAnimationController(
-        scrollbar_layer->ScrollLayerId());
+        scroll_layer_id, scrollbar_layer->ScrollElementId());
+  }
 
   DidUpdateScrollState(scrollbar_layer->ScrollLayerId());
 }
 
 void LayerTreeImpl::UnregisterScrollbar(
     ScrollbarLayerImplBase* scrollbar_layer) {
   int scroll_layer_id = scrollbar_layer->ScrollLayerId();
   if (scroll_layer_id == Layer::INVALID_ID)
     return;
 
   auto scrollbar_range = scrollbar_map_.equal_range(scroll_layer_id);
   for (auto i = scrollbar_range.first; i != scrollbar_range.second; ++i)
     if (i->second == scrollbar_layer->id()) {
       scrollbar_map_.erase(i);
       break;
     }
 
-  if (IsActiveTree() && scrollbar_map_.count(scroll_layer_id) == 0)
+  if (IsActiveTree() && scrollbar_map_.count(scroll_layer_id) == 0) {
     layer_tree_host_impl_->UnregisterScrollbarAnimationController(
-        scroll_layer_id);
+        scrollbar_layer->ScrollElementId());
+  }
 }
 
 ScrollbarSet LayerTreeImpl::ScrollbarsFor(int scroll_layer_id) const {
   ScrollbarSet scrollbars;
   auto scrollbar_range = scrollbar_map_.equal_range(scroll_layer_id);
   for (auto i = scrollbar_range.first; i != scrollbar_range.second; ++i)
     scrollbars.insert(LayerById(i->second)->ToScrollbarLayer());
   return scrollbars;
 }
 
@@ skipping 417 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc