Implements the dialog view for logout button tray in public sessions.

ash/system/logout_button/logout_button_tray.h

Index: ash/system/logout_button/logout_button_tray.h
diff --git a/ash/system/logout_button/logout_button_tray.h b/ash/system/logout_button/logout_button_tray.h
index 5683e5e2654c13f52e1d2e9efe0a9403e91b9cf2..2d9576ad8d00208386b6130c29fd073a979a66c3 100644
--- a/ash/system/logout_button/logout_button_tray.h
+++ b/ash/system/logout_button/logout_button_tray.h
@@ -10,6 +10,8 @@
 #include "ash/system/user/login_status.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
 #include "ui/views/controls/button/button.h"
 
 namespace views {
@@ -19,6 +21,7 @@ class LabelButton;
 namespace ash {
 namespace internal {
 
+class LogoutConfirmationDialogView;
 class StatusAreaWidget;
 
 // Adds a logout button to the launcher's status area if enabled by the
@@ -30,6 +33,9 @@ class LogoutButtonTray : public TrayBackgroundView,
   explicit LogoutButtonTray(StatusAreaWidget* status_area_widget);
   virtual ~LogoutButtonTray();
 
+  void EnsureConfirmationDialogIsShowing();
+  void EnsureConfirmationDialogIsClosed();
+
   // TrayBackgroundView:
   virtual void SetShelfAlignment(ShelfAlignment alignment) OVERRIDE;
   virtual base::string16 GetAccessibleNameForTray() OVERRIDE;
@@ -39,6 +45,7 @@ class LogoutButtonTray : public TrayBackgroundView,
 
   // LogoutButtonObserver:
   virtual void OnShowLogoutButtonInTrayChanged(bool show) OVERRIDE;
+  virtual void OnLogoutDialogDurationChanged(base::TimeDelta duration) OVERRIDE;
 
   // views::ButtonListener:
   virtual void ButtonPressed(views::Button* sender,
@@ -46,12 +53,17 @@ class LogoutButtonTray : public TrayBackgroundView,
 
   void UpdateAfterLoginStatusChange(user::LoginStatus login_status);
 
+  LogoutConfirmationDialogView* UnbindWithConfirmationDialog();

[bartfab (slow), 2013/11/20 18:00:44]

In general, the approach looks good but is overly complex:

* If the LogoutConfirmationDialogView is destroyed first, it would be sufficient
if it called a method named something like OnConfirmationDialogViewDestroyed()
which simply releases the confirmation_dialog_ pointer.

* You could make the LogoutConfirmationDialogView's owner_ pointer a WeakPtr.
LogoutButtonTray would have a weak_factory_ that this WeakPtr comes from. That
way, there would be no need to tell the dialog when its owner goes away. You
could then fold UnbindWithConfirmationDialog() into
EnsureConfirmationDialogIsClosed() and simplify it to:

void LogoutButtonTray::EnsureConfirmationDialogIsClosed() {
if (confirmation_dialog_) {
  weak_factory_.InvalidateWeakPtrs();
  confirmation_dialog_->GetWidget()->Close();
  base::MessageLoop::current()->DeleteSoon(FROM_HERE,
confirmation_dialog_.release());
}

Finally, three more nits:

1/ "Bind" has a very specific meaning in Chrome (it refers to base::Bind), so
you should not be using "bind" and "unbind" for naming unrelated methods.

2/ There is no need to warn that a method is not thread-safe. All Chrome code is
assumed to be non-thread-safe unless explicitly stated otherwise.

3/ The method is actually not atomic (i.e., it performs a sequence of
operations, not a single atomic one), so better do not document it as such :).

+
  private:
   void UpdateVisibility();
 
   views::LabelButton* button_;  // Not owned.
   user::LoginStatus login_status_;
   bool show_logout_button_in_tray_;
+  base::TimeDelta dialog_duration_;
+
+  scoped_ptr<LogoutConfirmationDialogView> confirmation_dialog_;
 
   DISALLOW_COPY_AND_ASSIGN(LogoutButtonTray);
 };