Re-land socket refactor with fixes for Windows.

runtime/bin/eventhandler_win.cc

Index: runtime/bin/eventhandler_win.cc
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index a6c16a6480f44e781d4f5de0fa485313ec5389f9..43a686d8536e7bbcc7d23afebd0df0262843834d 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -1570,7 +1570,7 @@ void EventHandlerImplementation::Start(EventHandler* handler) {
   }
 
   // Initialize Winsock32
-  if (!Socket::Initialize()) {
+  if (!SocketBase::Initialize()) {
     FATAL("Failed to initialized Windows sockets");
   }
 }