Closing simulation window in chromeos sessions causes crash.

ash/devtools/ash_devtools_dom_agent.cc

 // Copyright 2016 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 "ash/devtools/ash_devtools_dom_agent.h"
 
 #include "ash/devtools/ui_element.h"
 #include "ash/devtools/view_element.h"
 #include "ash/devtools/widget_element.h"
 #include "ash/devtools/window_element.h"
@@ skipping 203 matching lines @@
     observer.OnNodeBoundsChanged(node_id);
 }
 
 std::unique_ptr<ui::devtools::protocol::DOM::Node>
 AshDevToolsDOMAgent::BuildInitialTree() {
   is_building_tree_ = true;
   std::unique_ptr<Array<DOM::Node>> children = Array<DOM::Node>::create();
 
   // TODO(thanhph): Root of UIElement tree shoudn't be WindowElement
   // but maybe a new different element type.
-  window_element_root_ = new WindowElement(nullptr, this, nullptr);
+  window_element_root_ =
+      base::MakeUnique<WindowElement>(nullptr, this, nullptr);
 
   for (aura::Window* window : Shell::GetAllRootWindows()) {
     UIElement* window_element =
-        new WindowElement(window, this, window_element_root_);
+        new WindowElement(window, this, window_element_root_.get());
 
     children->addItem(BuildTreeForUIElement(window_element));
     window_element_root_->AddChild(window_element);
   }
   std::unique_ptr<ui::devtools::protocol::DOM::Node> root_node = BuildNode(
       "root", nullptr, std::move(children), window_element_root_->node_id());
   is_building_tree_ = false;
   return root_node;
 }
 
@@ skipping 77 matching lines @@
 void AshDevToolsDOMAgent::RemoveDomNode(UIElement* ui_element) {
   for (auto* child_element : ui_element->children())
     RemoveDomNode(child_element);
   frontend()->childNodeRemoved(ui_element->parent()->node_id(),
                                ui_element->node_id());
 }
 
 void AshDevToolsDOMAgent::Reset() {
   is_building_tree_ = false;
   widget_for_highlighting_.reset();
-  delete window_element_root_;
+  window_element_root_.reset();
   node_id_to_ui_element_.clear();
   observers_.Clear();
 }
 
 void AshDevToolsDOMAgent::InitializeHighlightingWidget() {
   DCHECK(!widget_for_highlighting_);
   widget_for_highlighting_.reset(new views::Widget);
   views::Widget::InitParams params;
   params.type = views::Widget::InitParams::TYPE_WINDOW_FRAMELESS;
   params.activatable = views::Widget::InitParams::ACTIVATABLE_NO;
@@ skipping 48 matching lines @@
   UpdateHighlight(window_and_bounds, content_color, border_color);
 
   if (!widget_for_highlighting_->IsVisible())
     widget_for_highlighting_->Show();
 
   return ui::devtools::protocol::Response::OK();
 }
 
 }  // namespace devtools
 }  // namespace ash