Make --install-chrome-app use extensions::WebstoreInstallWithPrompt.

chrome/browser/apps/install_chrome_app.h

Index: chrome/browser/apps/install_chrome_app.h
diff --git a/chrome/browser/apps/install_chrome_app.h b/chrome/browser/apps/install_chrome_app.h
deleted file mode 100644
index d14e90f53785c947a8e9ff74a710988519e94081..0000000000000000000000000000000000000000
--- a/chrome/browser/apps/install_chrome_app.h
+++ /dev/null
@@ -1,18 +0,0 @@
-// 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.
-
-#ifndef CHROME_BROWSER_APPS_INSTALL_CHROME_APP_H_
-#define CHROME_BROWSER_APPS_INSTALL_CHROME_APP_H_
-
-#include <string>
-
-namespace install_chrome_app {
-
-// Initiates the UI flow for installing a Chrome app.
-// Currently this is done by directing the user to the webstore page.
-void InstallChromeApp(const std::string& app_id);
-
-}  // namespace install_chrome_app
-
-#endif  // CHROME_BROWSER_APPS_INSTALL_CHROME_APP_H_