Revert of cc : Make LayerImpl destruction independent of tree hierarchy

cc/trees/layer_tree_host_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_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1197 matching lines @@
 void LayerTreeHostImpl::EvictTexturesForTesting() {
   UpdateTileManagerMemoryPolicy(ManagedMemoryPolicy(0));
 }
 
 void LayerTreeHostImpl::BlockNotifyReadyToActivateForTesting(bool block) {
   NOTREACHED();
 }
 
 void LayerTreeHostImpl::ResetTreesForTesting() {
   if (active_tree_)
-    active_tree_->DetachLayers();
+    active_tree_->ClearLayers();
   active_tree_ =
       LayerTreeImpl::create(this, active_tree()->page_scale_factor(),
                             active_tree()->top_controls_shown_ratio(),
                             active_tree()->elastic_overscroll());
   active_tree_->property_trees()->is_active = true;
   if (pending_tree_)
-    pending_tree_->DetachLayers();
+    pending_tree_->ClearLayers();
   pending_tree_ = nullptr;
   pending_tree_duration_timer_ = nullptr;
   if (recycle_tree_)
-    recycle_tree_->DetachLayers();
+    recycle_tree_->ClearLayers();
   recycle_tree_ = nullptr;
 }
 
 size_t LayerTreeHostImpl::SourceAnimationFrameNumberForTesting() const {
   return fps_counter_->current_frame_number();
 }
 
 void LayerTreeHostImpl::UpdateTileManagerMemoryPolicy(
     const ManagedMemoryPolicy& policy) {
   if (!resource_pool_)
@@ skipping 2807 matching lines @@
     const {
   return fixed_raster_scale_attempted_scale_change_history_.count() >=
          kFixedRasterScaleAttemptedScaleChangeThreshold;
 }
 
 void LayerTreeHostImpl::SetFixedRasterScaleAttemptedToChangeScale() {
   fixed_raster_scale_attempted_scale_change_history_.set(0);
 }
 
 }  // namespace cc