Revert of cc: Add a main thread LayerListIterator

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 420 matching lines @@
 
   if (hud_layer())
     target_tree->set_hud_layer(static_cast<HeadsUpDisplayLayerImpl*>(
         target_tree->LayerById(hud_layer()->id())));
   else
     target_tree->set_hud_layer(NULL);
 
   target_tree->has_ever_been_drawn_ = false;
 }
 
-LayerListIterator<LayerImpl> LayerTreeImpl::begin() {
-  return LayerListIterator<LayerImpl>(root_layer_);
+LayerListIterator LayerTreeImpl::begin() {
+  return LayerListIterator(root_layer_);
 }
 
-LayerListIterator<LayerImpl> LayerTreeImpl::end() {
-  return LayerListIterator<LayerImpl>(nullptr);
+LayerListIterator LayerTreeImpl::end() {
+  return LayerListIterator(nullptr);
 }
 
-LayerListReverseIterator<LayerImpl> LayerTreeImpl::rbegin() {
-  return LayerListReverseIterator<LayerImpl>(root_layer_);
+LayerListReverseIterator LayerTreeImpl::rbegin() {
+  return LayerListReverseIterator(root_layer_);
 }
 
-LayerListReverseIterator<LayerImpl> LayerTreeImpl::rend() {
-  return LayerListReverseIterator<LayerImpl>(nullptr);
+LayerListReverseIterator LayerTreeImpl::rend() {
+  return LayerListReverseIterator(nullptr);
 }
 
 void LayerTreeImpl::AddToElementMap(LayerImpl* layer) {
   if (!layer->element_id() || !layer->mutable_properties())
     return;
 
   TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
                "LayerTreeImpl::AddToElementMap", "element_id",
                layer->element_id(), "layer_id", layer->id());
 
@@ skipping 1640 matching lines @@
 }
 
 void LayerTreeImpl::ResetAllChangeTracking(PropertyTrees::ResetFlags flag) {
   layers_that_should_push_properties_.clear();
   for (auto* layer : *this)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking(flag);
 }
 
 }  // namespace cc