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

chrome/browser/extensions/startup_helper.h

 // Copyright (c) 2012 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_EXTENSIONS_STARTUP_HELPER_H_
 #define CHROME_BROWSER_EXTENSIONS_STARTUP_HELPER_H_
 
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/extensions/pack_extension_job.h"
 
@@ skipping 35 matching lines @@
   // Handle --limited-install-from-webstore flag from |cmd_line| by downloading
   // metadata from the webstore for the given id, prompting the user to
   // confirm, and then downloading the crx and installing it.
   // This whole process is only kicked off by this function and completed
   // asynchronously unlike InstallFromWebstore which finishes everything before
   // returning.
   void LimitedInstallFromWebstore(const base::CommandLine& cmd_line,
                                   Profile* profile,
                                   base::Callback<void()> done_callback);
 
+  // Handle --install-chrome-app flag from |cmd_line| by downloading metadata
+  // from the webstore for the given id, prompting the user to confirm, and then
+  // downloading the crx and installing it.
+  // Like InstallFromWebstore but this is asynchronous.
+  void InstallChromeApp(const base::CommandLine& cmd_line, Profile* profile);
+
   // Maps the command line argument to the extension id. Returns an empty string
   // in the case when there is no mapping.
   std::string WebStoreIdFromLimitedInstallCmdLine(
       const base::CommandLine& cmd_line);
  private:
   scoped_refptr<PackExtensionJob> pack_job_;
   bool pack_job_succeeded_;
 
   DISALLOW_COPY_AND_ASSIGN(StartupHelper);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_STARTUP_HELPER_H_