Added synchronous socket implementation to dart:io.

runtime/bin/eventhandler_win.h

Index: runtime/bin/eventhandler_win.h
diff --git a/runtime/bin/eventhandler_win.h b/runtime/bin/eventhandler_win.h
index 93dd44c3edc2d5cf8d337b5f71bcc39ad851d34e..112e541d243d397ebb3374ba599af68b87226466 100644
--- a/runtime/bin/eventhandler_win.h
+++ b/runtime/bin/eventhandler_win.h
@@ -446,12 +446,14 @@ class ListenSocket : public DescriptorInfoMultipleMixin<SocketHandle> {
 // Information on connected sockets.
 class ClientSocket : public DescriptorInfoSingleMixin<SocketHandle> {
  public:
-  explicit ClientSocket(intptr_t s)
+  explicit ClientSocket(intptr_t s, bool sync = false)

[zra, 2017/04/10 21:39:42]

Let's remove the Windows implementation from this CL.

[bkonyi, 2017/04/11 01:30:50]

Thought I had done this before. Removed.

       : DescriptorInfoSingleMixin(s, true),
         DisconnectEx_(NULL),
         next_(NULL),
         connected_(false),
-        closed_(false) {
+        closed_(false),
+        sync_(sync),
+  {
     LoadDisconnectEx();
     type_ = kClientSocket;
   }
@@ -497,6 +499,7 @@ class ClientSocket : public DescriptorInfoSingleMixin<SocketHandle> {
   ClientSocket* next_;
   bool connected_;
   bool closed_;
+  bool sync_;
 
 #if defined(DEBUG)
   static intptr_t disconnecting_;