Add ShellDelegate, MediaDelegate and KeyboardUI stubs to mus ash

ash/aura/wm_shell_aura.cc

Index: ash/aura/wm_shell_aura.cc
diff --git a/ash/aura/wm_shell_aura.cc b/ash/aura/wm_shell_aura.cc
index 19871636cb123b25a6d12df475787fc7ca58e342..c5a4db581aa332738d9ff87ba3c1e542f71c9f24 100644
--- a/ash/aura/wm_shell_aura.cc
+++ b/ash/aura/wm_shell_aura.cc
@@ -4,6 +4,8 @@
 
 #include "ash/aura/wm_shell_aura.h"
 
+#include <utility>
+
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_delegate.h"
@@ -38,7 +40,8 @@
 
 namespace ash {
 
-WmShellAura::WmShellAura(ShellDelegate* delegate) : WmShell(delegate) {
+WmShellAura::WmShellAura(std::unique_ptr<ShellDelegate> shell_delegate)
+    : WmShell(std::move(shell_delegate)) {
   WmShell::Set(this);
 }