CrOS: Add firmware version to about://version

chrome/browser/ui/webui/version_handler_chromeos.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_UI_WEBUI_VERSION_HANDLER_CHROMEOS_H_
 #define CHROME_BROWSER_UI_WEBUI_VERSION_HANDLER_CHROMEOS_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/ui/webui/version_handler.h"
 #include "chromeos/system/version_loader.h"
 
 // VersionHandlerChromeOS is responsible for loading the Chrome OS
 // version.
 class VersionHandlerChromeOS : public VersionHandler {
  public:
   VersionHandlerChromeOS();
   ~VersionHandlerChromeOS() override;
 
   // VersionHandler overrides:
   void HandleRequestVersionInfo(const base::ListValue* args) override;
 
   // Callbacks from chromeos::VersionLoader.
   void OnVersion(const std::string& version);
+  void OnOSFirmware(const std::string& version);
   void OnARCVersion(const std::string& version);
 
  private:
   base::WeakPtrFactory<VersionHandlerChromeOS> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VersionHandlerChromeOS);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_VERSION_HANDLER_CHROMEOS_H_