cc: DCHECK that the OutputSurface was released in ~LayerTreeHostImpl().

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 257 matching lines @@
                                  settings.top_controls_show_threshold,
                                  settings.top_controls_hide_threshold);
 }
 
 LayerTreeHostImpl::~LayerTreeHostImpl() {
   DCHECK(task_runner_provider_->IsImplThread());
   TRACE_EVENT0("cc", "LayerTreeHostImpl::~LayerTreeHostImpl()");
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerTreeHostImpl", id_);
 
+  // It is released before shutdown.
+  DCHECK(!output_surface_);
+
   if (input_handler_client_) {
     input_handler_client_->WillShutdown();
     input_handler_client_ = NULL;
   }
   if (scroll_elasticity_helper_)
     scroll_elasticity_helper_.reset();
 
   // The layer trees must be destroyed before the layer tree host. We've
   // made a contract with our animation controllers that the animation_host
   // will outlive them, and we must make good.
   if (recycle_tree_)
     recycle_tree_->Shutdown();
   if (pending_tree_)
     pending_tree_->Shutdown();
   active_tree_->Shutdown();
   recycle_tree_ = nullptr;
   pending_tree_ = nullptr;
   active_tree_ = nullptr;
 
   animation_host_->ClearTimelines();
   animation_host_->SetMutatorHostClient(nullptr);
 
   CleanUpTileManagerAndUIResources();
   renderer_ = nullptr;
   resource_provider_ = nullptr;
-
-  if (output_surface_) {
-    output_surface_->DetachFromClient();
-    output_surface_ = nullptr;
-  }
 }
 
 void LayerTreeHostImpl::BeginMainFrameAborted(CommitEarlyOutReason reason) {
   // If the begin frame data was handled, then scroll and scale set was applied
   // by the main thread, so the active tree needs to be updated as if these sent
   // values were applied and committed.
   if (CommitEarlyOutHandledCommit(reason))
     active_tree_->ApplySentScrollAndScaleDeltasFromAbortedCommit();
 }
 
@@ skipping 3692 matching lines @@
   return task_runner_provider_->HasImplThread();
 }
 
 bool LayerTreeHostImpl::CommitToActiveTree() const {
   // In single threaded mode we skip the pending tree and commit directly to the
   // active tree.
   return !task_runner_provider_->HasImplThread();
 }
 
 }  // namespace cc