mash: Introduce ShowWebDialogWithContainer for webui dialogs

chrome/browser/chromeos/set_time_dialog.h

Index: chrome/browser/chromeos/set_time_dialog.h
diff --git a/chrome/browser/chromeos/set_time_dialog.h b/chrome/browser/chromeos/set_time_dialog.h
index e0970b7ecd51079f954d0a475f27ca5e6fbf7579..028da61ec018edb5d78ce35b3efd05d8bad622e0 100644
--- a/chrome/browser/chromeos/set_time_dialog.h
+++ b/chrome/browser/chromeos/set_time_dialog.h
@@ -18,12 +18,18 @@ namespace chromeos {
 // Set Time dialog for setting the system time, date and time zone.
 class SetTimeDialog : public ui::WebDialogDelegate {
  public:
-  SetTimeDialog();
-  ~SetTimeDialog() override;
+  // Shows the dialog as a child of |parent|, for example the webui settings
+  // window.
+  static void ShowDialogInParent(gfx::NativeWindow parent);
 
-  static void ShowDialog(gfx::NativeWindow owning_window);
+  // Shows the dialog in a given container, for example at the login screen
+  // where the general settings window is not available.
+  static void ShowDialogInContainer(int container_id);
 
  private:
+  SetTimeDialog();
+  ~SetTimeDialog() override;
+
   // ui::WebDialogDelegate:
   ui::ModalType GetDialogModalType() const override;
   base::string16 GetDialogTitle() const override;