[headless] Use version for product name and user agent.

headless/lib/headless_content_client.h

 // Copyright 2015 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 HEADLESS_LIB_HEADLESS_CONTENT_CLIENT_H_
 #define HEADLESS_LIB_HEADLESS_CONTENT_CLIENT_H_
 
 #include "content/public/common/content_client.h"
 #include "headless/public/headless_browser.h"
 
 namespace headless {
 
 class HeadlessContentClient : public content::ContentClient {
  public:
   explicit HeadlessContentClient(HeadlessBrowser::Options* options);
   ~HeadlessContentClient() override;
 
   // content::ContentClient implementation:
+  std::string GetProduct() const override;
   std::string GetUserAgent() const override;
   base::string16 GetLocalizedString(int message_id) const override;
   base::StringPiece GetDataResource(
       int resource_id,
       ui::ScaleFactor scale_factor) const override;
   base::RefCountedMemory* GetDataResourceBytes(
       int resource_id) const override;
   gfx::Image& GetNativeImageNamed(int resource_id) const override;
 
  private:
   HeadlessBrowser::Options* options_;  // Not owned.
 
   DISALLOW_COPY_AND_ASSIGN(HeadlessContentClient);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_LIB_HEADLESS_CONTENT_CLIENT_H_