Added synchronous socket implementation to dart:io.

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 43a686d8536e7bbcc7d23afebd0df0262843834d..2309ec80cb16ae5a9d750707fa82bef01c7e065a 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -937,8 +937,9 @@ bool ClientSocket::IssueRead() {
 
   DWORD flags;
   flags = 0;
+  OVERLAPPED* overlap_buffer = (sync ? NULL : buffer->GetCleanOverlapped());
   int rc = WSARecv(socket(), buffer->GetWASBUF(), 1, NULL, &flags,
-                   buffer->GetCleanOverlapped(), NULL);
+                   overlap_buffer, NULL);
   if ((rc == NO_ERROR) || (WSAGetLastError() == WSA_IO_PENDING)) {
     pending_read_ = buffer;
     return true;
@@ -956,8 +957,10 @@ bool ClientSocket::IssueWrite() {
   ASSERT(pending_write_ != NULL);
   ASSERT(pending_write_->operation() == OverlappedBuffer::kWrite);
 
+  OVERLAPPED* overlap_buffer =
+      (sync ? NULL : pending_write->GetCleanOverlapped());
   int rc = WSASend(socket(), pending_write_->GetWASBUF(), 1, NULL, 0,
-                   pending_write_->GetCleanOverlapped(), NULL);
+                   overlap_buffer, NULL);
   if ((rc == NO_ERROR) || (WSAGetLastError() == WSA_IO_PENDING)) {
     return true;
   }
@@ -970,8 +973,8 @@ bool ClientSocket::IssueWrite() {
 
 void ClientSocket::IssueDisconnect() {
   OverlappedBuffer* buffer = OverlappedBuffer::AllocateDisconnectBuffer();
-  BOOL ok =
-      DisconnectEx_(socket(), buffer->GetCleanOverlapped(), TF_REUSE_SOCKET, 0);
+  OVERLAPPED* overlap_buffer = (sync ? NULL : buffer->GetCleanOverlapped());
+  BOOL ok = DisconnectEx_(socket(), overlap_buffer, TF_REUSE_SOCKET, 0);
   // DisconnectEx works like other OverlappedIO APIs, where we can get either an
   // immediate success or delayed operation by WSA_IO_PENDING being set.
   if (ok || (WSAGetLastError() != WSA_IO_PENDING)) {