Improve doc of ViewObserver and clarify arguments

ui/views/view_unittest.cc

 // Copyright (c) 2012 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 "ui/views/view.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
@@ skipping 4860 matching lines @@
         child_view_removed_(nullptr),
         child_view_removed_parent_(nullptr),
         view_visibility_changed_(nullptr),
         view_enabled_changed_(nullptr),
         view_bounds_changed_(nullptr),
         view_reordered_(nullptr) {}
 
   ~ViewObserverTest() override {}
 
   // ViewObserver:
-  void OnChildViewAdded(View* child) override {
+  void OnChildViewAdded(View* parent, View* child) override {

[Bret, 2017/03/14 18:58:36]

add a couple lines to the existing unit tests that verify the parent argument is
actually the parent, for this and OnChildViewReordered below

[sky, 2017/03/14 20:19:28]

Done.

     child_view_added_times_++;
     child_view_added_ = child;
   }
-  void OnChildViewRemoved(View* child, View* parent) override {
+  void OnChildViewRemoved(View* parent, View* child) override {
     child_view_removed_times_++;
     child_view_removed_ = child;
     child_view_removed_parent_ = parent;
   }
 
   void OnViewVisibilityChanged(View* view) override {
     view_visibility_changed_ = view;
   }
 
   void OnViewEnabledChanged(View* view) override {
     view_enabled_changed_ = view;
   }
 
   void OnViewBoundsChanged(View* view) override { view_bounds_changed_ = view; }
 
-  void OnChildViewReordered(View* view) override { view_reordered_ = view; }
+  void OnChildViewReordered(View* parent, View* view) override {
+    view_reordered_ = view;
+  }
 
   void reset() {
     child_view_added_times_ = 0;
     child_view_removed_times_ = 0;
     child_view_added_ = nullptr;
     child_view_removed_ = nullptr;
     child_view_removed_parent_ = nullptr;
     view_visibility_changed_ = nullptr;
     view_enabled_changed_ = nullptr;
     view_bounds_changed_ = nullptr;
@@ skipping 98 matching lines @@
   std::unique_ptr<View> view = NewView();
   std::unique_ptr<View> child_view = NewView();
   std::unique_ptr<View> child_view2 = NewView();
   view->AddChildView(child_view.get());
   view->AddChildView(child_view2.get());
   view->ReorderChildView(child_view2.get(), 0);
   EXPECT_EQ(child_view2.get(), view_reordered());
 }
 
 }  // namespace views