Revert of Removing HTTPS and SOCKS proxy server code.

webrtc/base/proxyserver.h

Index: webrtc/base/proxyserver.h
diff --git a/webrtc/base/proxyserver.h b/webrtc/base/proxyserver.h
index 1622daf13b347b508566504444abf5160116de79..86007c3606fc33443cdbc63c3c1916493a047686 100644
--- a/webrtc/base/proxyserver.h
+++ b/webrtc/base/proxyserver.h
@@ -83,6 +83,18 @@ class ProxyServer : public sigslot::has_slots<> {
   RTC_DISALLOW_COPY_AND_ASSIGN(ProxyServer);
 };
 
+// SocksProxyServer is a simple extension of ProxyServer to implement SOCKS.
+class SocksProxyServer : public ProxyServer {
+ public:
+  SocksProxyServer(SocketFactory* int_factory, const SocketAddress& int_addr,
+                   SocketFactory* ext_factory, const SocketAddress& ext_ip)
+      : ProxyServer(int_factory, int_addr, ext_factory, ext_ip) {
+  }
+ protected:
+  AsyncProxyServerSocket* WrapSocket(AsyncSocket* socket) override;
+  RTC_DISALLOW_COPY_AND_ASSIGN(SocksProxyServer);
+};
+
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_PROXYSERVER_H_