Giving focus to an app shim brings windows belonging to that app to the foreground.

ui/base/cocoa/focus_window_set.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_BASE_COCOA_FOCUS_WINDOW_SET_H_
+#define UI_BASE_COCOA_FOCUS_WINDOW_SET_H_
+
+#include <set>
+
+#include "ui/base/ui_export.h"
+#include "ui/gfx/native_widget_types.h"
+
+namespace ui {
+
+// Brings a group of windows to the front without changing their order, and
+// makes the frontmost one key and main.
+UI_EXPORT void FocusWindowSet(std::set<gfx::NativeWindow> windows);
+
+}  // namespace ui
+
+#endif  // UI_BASE_COCOA_FOCUS_WINDOW_SET_H_