cc: Replace LayerIterator with iterator that walks layer list and effect tree

cc/layers/layer_impl.cc

 // Copyright 2012 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/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 926 matching lines @@
 }
 
 RenderSurfaceImpl* LayerImpl::render_target() {
   return GetEffectTree().GetRenderSurface(render_target_effect_tree_index());
 }
 
 const RenderSurfaceImpl* LayerImpl::render_target() const {
   return GetEffectTree().GetRenderSurface(render_target_effect_tree_index());
 }
 
-bool LayerImpl::IsHidden() const {
-  EffectNode* node = GetEffectTree().Node(effect_tree_index_);
-  return node->screen_space_opacity == 0.f;
-}
-
 float LayerImpl::GetIdealContentsScale() const {
   float page_scale = IsAffectedByPageScale()
                          ? layer_tree_impl()->current_page_scale_factor()
                          : 1.f;
   float device_scale = layer_tree_impl()->device_scale_factor();
 
   float default_scale = page_scale * device_scale;
   if (!layer_tree_impl()
            ->settings()
            .layer_transforms_should_scale_layer_contents) {
@@ skipping 19 matching lines @@
 
 ScrollTree& LayerImpl::GetScrollTree() const {
   return GetPropertyTrees()->scroll_tree;
 }
 
 TransformTree& LayerImpl::GetTransformTree() const {
   return GetPropertyTrees()->transform_tree;
 }
 
 }  // namespace cc