Ensure default dialog button focus remains after a dialog update.

ui/views/window/dialog_client_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.
 
 #include "ui/views/window/dialog_client_view.h"
 
 #include <algorithm>
 
 #include "build/build_config.h"
 #include "ui/base/material_design/material_design_controller.h"
@@ skipping 301 matching lines @@
   View* third = ok_button_;
   if (kIsOkButtonOnLeftSide)
     std::swap(second, third);
   return {{first, second, third}};
 }
 
 void DialogClientView::SetupLayout() {
   base::AutoReset<bool> auto_reset(&adding_or_removing_views_, true);
   GridLayout* layout = new GridLayout(button_row_container_);
   layout->set_minimum_size(minimum_size_);
+  default_focus_ = GetDialogDelegate()->GetInitiallyFocusedView();

[sky, 2017/04/28 20:49:52]

There should be no need for the member as it's only used in this function. I
think you need to do the following:

You'll need null checks here!

View* focused_view = GetFocusManager()->GetFocusedView();
Then add an observer on focused_view.

reset of function

at end:
// You'll need null check here too!
if (!GetFocusManager()->GetFocusedView() && focused_view)
  focused_view->RequestFocus();

The observer tracks OnViewIsDeleting and sets focused_view to null. This is
necessary as SetupLayout has side effects that could do weird things.

[ackermanb, 2017/05/17 17:20:54]

Done.

 
   // Clobber any existing LayoutManager since it has weak references to child
   // Views which may be removed by SetupViews().
   button_row_container_->SetLayoutManager(layout);
   SetupViews();
   const std::array<View*, kNumButtons> views = GetButtonRowViews();
 
   // Visibility changes on |extra_view_| must be observed to re-Layout. However,
   // when hidden it's not included in the button row (it can't influence layout)
   // and it can't be added to |button_row_container_| (GridLayout complains).
@@ skipping 60 matching lines @@
   }
 
   if (ui::MaterialDesignController::IsSecondaryUiMaterial()) {
     // Only link the extra view column if it is a button.
     if (views[0] && !CustomButton::AsCustomButton(views[0]))
       column_set->LinkColumnSizes(link[1], link[2], -1);
     else
       column_set->LinkColumnSizes(link[0], link[1], link[2], -1);
   }
   layout->AddPaddingRow(kFixed, insets.bottom());
+
+  // The default focus is lost when child views are added back into the dialog.
+  // This restores focus to the default.
+  if (default_focus_) {
+    default_focus_->RequestFocus();
+  }
 }
 
 void DialogClientView::SetupViews() {
   button_row_container_->RemoveAllChildViews(false /* delete children */);
   // If SetupLayout() "stored" a hidden |extra_view_| in |this|, ensure it can
   // be re-added to the layout when becoming visible.
   if (extra_view_)
     RemoveChildView(extra_view_);
 
   UpdateDialogButton(&ok_button_, ui::DIALOG_BUTTON_OK);
   UpdateDialogButton(&cancel_button_, ui::DIALOG_BUTTON_CANCEL);
 
   if (extra_view_)
     return;
 
   extra_view_ = GetDialogDelegate()->CreateExtraView();
   if (extra_view_)
     extra_view_->SetGroup(kButtonGroup);
 }
 
 }  // namespace views