Make the virtual keyboard show up on the display with input focus.

ash/mus/keyboard_ui_mus.h

Index: ash/mus/keyboard_ui_mus.h
diff --git a/ash/mus/keyboard_ui_mus.h b/ash/mus/keyboard_ui_mus.h
index 4c31f3044ff4487085ea4fe8c93de08469385b81..ea4bbda8bae7fdef7dcae14ebccbd99426f5e486 100644
--- a/ash/mus/keyboard_ui_mus.h
+++ b/ash/mus/keyboard_ui_mus.h
@@ -5,6 +5,8 @@
 #ifndef ASH_MUS_KEYBOARD_UI_MUS_H_
 #define ASH_MUS_KEYBOARD_UI_MUS_H_
 
+#include <stdint.h>
+
 #include <memory>
 
 #include "ash/common/keyboard/keyboard_ui.h"
@@ -30,6 +32,7 @@ class KeyboardUIMus : public KeyboardUI,
   // KeyboardUI:
   void Hide() override;
   void Show() override;
+  void ShowInDisplay(const int64_t display_id) override;
   bool IsEnabled() override;
 
   // keyboard::mojom::KeyboardObserver: