HTTPDownloader: Drop user agent from base class

src/frontend-common/http_downloader.h

@@ -75,7 +75,6 @@ protected:
   u32 LockedGetActiveRequestCount();
   void LockedPollRequests(std::unique_lock<std::mutex>& lock);
 
-  std::string m_user_agent;
   float m_timeout;
   u32 m_max_active_requests;
 

src/frontend-common/http_downloader_winhttp.cpp

@@ -37,7 +37,7 @@ bool HTTPDownloaderWinHttp::Initialize(const char* user_agent)
   const DWORD dwAccessType =
     IsWindows8Point1OrGreater() ? WINHTTP_ACCESS_TYPE_AUTOMATIC_PROXY : WINHTTP_ACCESS_TYPE_DEFAULT_PROXY;
 
-  m_hSession = WinHttpOpen(StringUtil::UTF8StringToWideString(m_user_agent).c_str(), dwAccessType, nullptr, nullptr,
+  m_hSession = WinHttpOpen(StringUtil::UTF8StringToWideString(user_agent).c_str(), dwAccessType, nullptr, nullptr,
                            WINHTTP_FLAG_ASYNC);
   if (m_hSession == NULL)
   {