Move app.window API implementation to extensions

extensions/shell/browser/shell_web_contents_modal_dialog_manager.cc

+// Copyright 2014 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.
+
+#include "components/web_modal/web_contents_modal_dialog_manager.h"
+
+namespace web_modal {
+
+SingleWebContentsDialogManager*
+WebContentsModalDialogManager::CreateNativeWebModalManager(
+    NativeWebContentsModalDialog dialog,
+    SingleWebContentsDialogManagerDelegate* native_delegate) {
+  // TODO(oshima): Investigate if we need to implement this.
+  NOTREACHED();
+  return NULL;
+}
+
+}  // namespace web_modal