Improve doc of ViewObserver and clarify arguments

ash/common/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/common/devtools/ash_devtools_dom_agent.h"
 
 #include "ash/common/wm_window.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
@@ skipping 167 matching lines @@
   if (view == widget->GetRootView())
     RemoveViewTree(view, nullptr, true);
 }
 
 void AshDevToolsDOMAgent::OnWidgetBoundsChanged(views::Widget* widget,
                                                 const gfx::Rect& new_bounds) {
   for (auto& observer : observers_)
     observer.OnWidgetBoundsChanged(widget);
 }
 
-void AshDevToolsDOMAgent::OnChildViewRemoved(views::View* view,
-                                             views::View* parent) {
+void AshDevToolsDOMAgent::OnChildViewRemoved(views::View* parent,
+                                             views::View* view) {
   RemoveViewTree(view, parent, true);
 }
 
-void AshDevToolsDOMAgent::OnChildViewAdded(views::View* view) {
+void AshDevToolsDOMAgent::OnChildViewAdded(views::View* parent,
+                                           views::View* view) {
   AddViewTree(view);
 }
 
-void AshDevToolsDOMAgent::OnChildViewReordered(views::View* view) {
-  RemoveViewTree(view, view->parent(), false);
+void AshDevToolsDOMAgent::OnChildViewReordered(views::View* parent,
+                                               views::View* view) {
+  RemoveViewTree(view, parent, false);
   AddViewTree(view);
 }
 
 void AshDevToolsDOMAgent::OnViewBoundsChanged(views::View* view) {
   for (auto& observer : observers_)
     observer.OnViewBoundsChanged(view);
 }
 
 WmWindow* AshDevToolsDOMAgent::GetWindowFromNodeId(int nodeId) {
   return node_id_to_window_map_.count(nodeId) ? node_id_to_window_map_[nodeId]
@@ skipping 313 matching lines @@
   return ui::devtools::protocol::Response::OK();
 }
 
 bool AshDevToolsDOMAgent::IsHighlightingWindow(WmWindow* window) {
   return widget_for_highlighting_ &&
          GetWidgetFromWmWindow(window) == widget_for_highlighting_.get();
 }
 
 }  // namespace devtools
 }  // namespace ash