Fix cc scrollbar layer issues with initialization, and use element ids throughout.

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 566 matching lines @@
                layer->element_id().AsValue().release(), "layer_id",
                layer->id());
 
   layer_tree_host_impl_->mutator_host()->UnregisterElement(
       layer->element_id(),
       IsActiveTree() ? ElementListType::ACTIVE : ElementListType::PENDING);
 
   element_layers_map_.erase(layer->element_id());
 }
 
-void LayerTreeImpl::AddToOpacityAnimationsMap(int id, float opacity) {
-  if (LayerImpl* layer = LayerById(id))
-    element_id_to_opacity_animations_[layer->element_id()] = opacity;
-}
-
 void LayerTreeImpl::SetTransformMutated(ElementId element_id,
                                         const gfx::Transform& transform) {
   DCHECK_EQ(1u, property_trees()->element_id_to_transform_node_index.count(
                     element_id));
   element_id_to_transform_animations_[element_id] = transform;
   if (!property_trees()->transform_tree.OnTransformAnimated(element_id,
                                                             transform))
     return;
 
   if (LayerImpl* layer = LayerByElementId(element_id))
@@ skipping 806 matching lines @@
 
 gfx::Rect LayerTreeImpl::DeviceViewport() const {
   return layer_tree_host_impl_->DeviceViewport();
 }
 
 const gfx::Rect LayerTreeImpl::ViewportRectForTilePriority() const {
   return layer_tree_host_impl_->ViewportRectForTilePriority();
 }
 
 std::unique_ptr<ScrollbarAnimationController>
-LayerTreeImpl::CreateScrollbarAnimationController(ElementId scroll_element_id) {
+LayerTreeImpl::CreateScrollbarAnimationController(ElementId scroll_element_id,
+                                                  float initial_opacity) {
   DCHECK(!settings().scrollbar_fade_delay.is_zero());
   DCHECK(!settings().scrollbar_fade_duration.is_zero());
   base::TimeDelta fade_delay = settings().scrollbar_fade_delay;
   base::TimeDelta fade_duration = settings().scrollbar_fade_duration;
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::ANDROID_OVERLAY: {
       return ScrollbarAnimationController::
-          CreateScrollbarAnimationControllerAndroid(scroll_element_id,
-                                                    layer_tree_host_impl_,
-                                                    fade_delay, fade_duration);
+          CreateScrollbarAnimationControllerAndroid(
+              scroll_element_id, layer_tree_host_impl_, fade_delay,
+              fade_duration, initial_opacity);
     }
     case LayerTreeSettings::AURA_OVERLAY: {
       base::TimeDelta thinning_duration =
           settings().scrollbar_thinning_duration;
       return ScrollbarAnimationController::
           CreateScrollbarAnimationControllerAuraOverlay(
               scroll_element_id, layer_tree_host_impl_, fade_delay,
-              fade_duration, thinning_duration);
+              fade_duration, thinning_duration, initial_opacity);
     }
     case LayerTreeSettings::NO_ANIMATOR:
       NOTREACHED();
       break;
   }
   return nullptr;
 }
 
 void LayerTreeImpl::DidAnimateScrollOffset() {
   layer_tree_host_impl_->DidAnimateScrollOffset();
@@ skipping 217 matching lines @@
 
 void LayerTreeImpl::RegisterScrollbar(ScrollbarLayerImplBase* scrollbar_layer) {
   ElementId scroll_element_id = scrollbar_layer->scroll_element_id();
   if (!scroll_element_id)
     return;
 
   element_id_to_scrollbar_layer_ids_.insert(
       std::pair<ElementId, int>(scroll_element_id, scrollbar_layer->id()));
   if (IsActiveTree() && scrollbar_layer->is_overlay_scrollbar()) {
     layer_tree_host_impl_->RegisterScrollbarAnimationController(
-        scroll_element_id);
+        scroll_element_id, scrollbar_layer->Opacity());
   }
 
   // TODO(pdr): Refactor DidUpdateScrollState to use ElementIds instead of
   // layer ids and remove this use of LayerIdByElementId.
   DidUpdateScrollState(LayerIdByElementId(scroll_element_id));
 }
 
 void LayerTreeImpl::UnregisterScrollbar(
     ScrollbarLayerImplBase* scrollbar_layer) {
   ElementId scroll_element_id = scrollbar_layer->scroll_element_id();
@@ skipping 424 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