Ensure default dialog button focus remains after a dialog update.

ui/views/window/dialog_client_view.cc

Index: ui/views/window/dialog_client_view.cc
diff --git a/ui/views/window/dialog_client_view.cc b/ui/views/window/dialog_client_view.cc
index 5d543a7572efe2b85b8772f293c766cbdb19430f..f7096064a8f2cf3214478de36355beee767129e2 100644
--- a/ui/views/window/dialog_client_view.cc
+++ b/ui/views/window/dialog_client_view.cc
@@ -17,10 +17,39 @@
 #include "ui/views/controls/button/md_text_button.h"
 #include "ui/views/layout/grid_layout.h"
 #include "ui/views/style/platform_style.h"
+#include "ui/views/view_observer.h"
 #include "ui/views/views_delegate.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/window/dialog_delegate.h"
 
+namespace {

[sky, 2017/05/17 19:08:30]

Move this code to around line 80ish, inside the view namespace so you don't need
view:: everywhere.

[ackermanb, 2017/05/17 22:03:49]

Done.

+
+class ViewDeletionObserver : public views::ViewObserver {

[sky, 2017/05/17 19:08:30]

Add comment.

[ackermanb, 2017/05/17 22:03:50]

Done.

+ public:
+  ViewDeletionObserver(views::View* observed_view)

[sky, 2017/05/17 19:08:30]

explicit

[ackermanb, 2017/05/17 22:03:50]

Done.

+      : observed_view_(observed_view) {
+    if (observed_view_)
+      observed_view_->AddObserver(this);
+  }
+
+  ~ViewDeletionObserver() override {
+    if (observed_view_)
+      observed_view_->RemoveObserver(this);
+  }
+
+  void OnViewIsDeleting(views::View* observed_view) override {

[sky, 2017/05/17 19:08:30]

Prefix with:
// ViewObserver:

[ackermanb, 2017/05/17 22:03:50]

Done.

+    DCHECK_EQ(observed_view, observed_view_);
+    observed_view_ = nullptr;

[sky, 2017/05/17 19:08:30]

Remove observer here.

[ackermanb, 2017/05/17 22:03:49]

Done.

+  }
+
+  views::View* focused_view() { return observed_view_; }
+
+ private:
+  views::View* observed_view_ = nullptr;

[Devlin, 2017/05/17 18:13:49]

DISALLOW_COPY_AND_ASSIGN()

[ackermanb, 2017/05/17 22:03:50]

Done.

+};
+
+}  // namespace
+
 namespace views {
 
 namespace {
@@ -319,6 +348,7 @@ 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_);
+  ViewDeletionObserver deletion_observer(GetFocusManager()->GetFocusedView());

[Devlin, 2017/05/17 18:13:49]

nit: Since we use the FocusManager twice in this function, we can cache it in a
variable.

[ackermanb, 2017/05/17 22:03:50]

Done.

 
   // Clobber any existing LayoutManager since it has weak references to child
   // Views which may be removed by SetupViews().
@@ -399,6 +429,12 @@ void DialogClientView::SetupLayout() {
       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 if the button is still available.
+  View* focused_view = deletion_observer.focused_view();

[sky, 2017/05/17 19:08:30]

Name this previously_focused_view.

[ackermanb, 2017/05/17 22:03:50]

Done.

+  if (!GetFocusManager()->GetFocusedView() && focused_view)

[Devlin, 2017/05/17 18:13:49]

drive-by nit: I'd invert these, since checking focused_view is cheaper:
if (focused_view && !GetFocusManaged()->GetFocusedView())

[sky, 2017/05/17 19:08:30]

Also, add a conditional of Contains(focused_view);

[ackermanb, 2017/05/17 22:03:49]

Done.

[ackermanb, 2017/05/17 22:03:50]

Done.

+    focused_view->RequestFocus();
 }
 
 void DialogClientView::SetupViews() {