Fix escaping focus traversal from LoginUserMenu

Makes use of SetFocusTraversableParent to declare where focus should go
after the view has been fully traversed.

Fixes infinite recursion where LoginUserMenu would redirect focus to its
anchor and then forward focus (which takes it inside LoginUserMenu as
the dialog is anchored).

Bug: chromium:901456
Change-Id: I138be71866760de84980f5e4ca0c1b42d6d1793f
Reviewed-on: https://chromium-review.googlesource.com/c/1338222
Commit-Queue: Peter Boström <pbos@chromium.org>
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613367}

ash/login/ui/login_bubble.cc

@@ -36,6 +36,7 @@
 #include "ui/views/focus/focus_manager.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
+#include "ui/views/view_properties.h"
 #include "ui/wm/core/coordinate_conversion.h"
 
 namespace ash {
@@ -325,11 +326,24 @@ class LoginUserMenuView : public LoginBaseBubbleView,
       remove_user_button_->SetAccessibleName(remove_user_label_->text());
       container->AddChildView(remove_user_button_);
     }
+  }
+
+  void RequestFocus() override {
+    // This view has no actual interesting contents to focus, so immediately
+    // forward to the button.
+    if (remove_user_button_)
+      remove_user_button_->RequestFocus();
+  }
 
-    // The user menu is focusable so that the we can detect when to refocus the
-    // lock window from tab navigation, otherwise focus will be trapped inside
-    // of the bubble.
-    SetFocusBehavior(views::View::FocusBehavior::ALWAYS);
+  void AddedToWidget() override {
+    LoginBaseBubbleView::AddedToWidget();
+    // Set up focus traversable parent so that keyboard focus can continue in
+    // the lock window, otherwise focus will be trapped inside the bubble.
+    if (GetAnchorView()) {
+      GetWidget()->SetFocusTraversableParent(
+          anchor_widget()->GetFocusTraversable());
+      GetWidget()->SetFocusTraversableParentView(GetAnchorView());
+    }
   }
 
   ~LoginUserMenuView() override = default;
@@ -346,16 +360,6 @@ class LoginUserMenuView : public LoginBaseBubbleView,
     size.Enlarge(kUserMenuMarginWidth, 0);
     return size;
   }
-  void OnFocus() override {
-    // This view has no actual interesting contents to focus, so immediately
-    // forward to the button.
-    remove_user_button_->RequestFocus();
-  }
-  void AboutToRequestFocusFromTabTraversal(bool reverse) override {
-    // Redirect the focus event to the lock screen.
-    Shell::Get()->focus_cycler()->FocusWidget(LockScreen::Get()->window());
-    LockScreen::Get()->window()->GetFocusManager()->AdvanceFocus(reverse);
-  }
 
   // views::ButtonListener:
   void ButtonPressed(views::Button* sender, const ui::Event& event) override {
@@ -488,6 +492,7 @@ void LoginBubble::ShowUserMenu(const base::string16& username,
       this, username, email, type, is_owner, anchor_view, bubble_opener,
       show_remove_user, std::move(on_remove_user_warning_shown),
       std::move(on_remove_user_requested));
+  // Prevent focus from going into |bubble_view_|.
   bool had_focus = bubble_view_->GetBubbleOpener() &&
                    bubble_view_->GetBubbleOpener()->HasFocus();
   Show();