Added common layout framework for system menu rows.

ui/views/view.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.
 
 #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
 
 #include "ui/views/view.h"
 
 #include <algorithm>
 #include <cmath>
@@ skipping 110 matching lines @@
       native_view_accessibility_(NULL) {
   SetTargetHandler(this);
 }
 
 View::~View() {
   if (parent_)
     parent_->RemoveChildView(this);
 
   ViewStorage::GetInstance()->ViewRemoved(this);
 
+  // Some layout managers hold a reference to the host that they are installed

[sky, 2016/10/20 15:59:11]

I have a mild preference to move this after deleting the children. That's what
we do in ~Window. Does that work for your case?

[bruthig, 2016/10/20 19:01:34]

The risk in doing so is that View may try to access a deleted child but I was
able to include a test to guard against this so I've changed it as requested.

[sky, 2016/10/20 20:42:22]

Now that I look at this code again I think the way you had it is better, because
apparently we won't call LayoutManager::ViewRemoved() because of the parent =
NULL below. So, I think either move the reset where you had it, or make
ViewRemoved be called. Sorry for the run around.

[bruthig, 2016/10/20 21:00:48]

Done.

+  // to and may need to access this during destruction.
+  layout_manager_.reset();
+
   for (Views::const_iterator i(children_.begin()); i != children_.end(); ++i) {
     (*i)->parent_ = NULL;
     if (!(*i)->owned_by_client_)
       delete *i;
   }
 
   // Release ownership of the native accessibility object, but it's
   // reference-counted on some platforms, so it may not be deleted right away.
   if (native_view_accessibility_)
     native_view_accessibility_->Destroy();
@@ skipping 2277 matching lines @@
   // Message the RootView to do the drag and drop. That way if we're removed
   // the RootView can detect it and avoid calling us back.
   gfx::Point widget_location(event.location());
   ConvertPointToWidget(this, &widget_location);
   widget->RunShellDrag(this, data, widget_location, drag_operations, source);
   // WARNING: we may have been deleted.
   return true;
 }
 
 }  // namespace views