mash: Port mojo:ash_sysui's ContextMenuMus to mojo:ash.

chrome/browser/ui/ash/chrome_shell_delegate.h

Index: chrome/browser/ui/ash/chrome_shell_delegate.h
diff --git a/chrome/browser/ui/ash/chrome_shell_delegate.h b/chrome/browser/ui/ash/chrome_shell_delegate.h
index 50f716dfbeecb22a489d849c3f605c1d651db10f..8c053bc5389aca7ab304d666538f7cccf3e9ed44 100644
--- a/chrome/browser/ui/ash/chrome_shell_delegate.h
+++ b/chrome/browser/ui/ash/chrome_shell_delegate.h
@@ -46,7 +46,7 @@ class ChromeShellDelegate : public ash::ShellDelegate,
   app_list::AppListPresenter* GetAppListPresenter() override;
   ash::ShelfDelegate* CreateShelfDelegate(ash::ShelfModel* model) override;
   ash::SystemTrayDelegate* CreateSystemTrayDelegate() override;
-  ash::UserWallpaperDelegate* CreateUserWallpaperDelegate() override;
+  std::unique_ptr<ash::WallpaperDelegate> CreateWallpaperDelegate() override;
   ash::SessionStateDelegate* CreateSessionStateDelegate() override;
   ash::AccessibilityDelegate* CreateAccessibilityDelegate() override;
   ash::NewWindowDelegate* CreateNewWindowDelegate() override;