Extend dart:io error handling to all socket functions

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 cfc0d8c14261a3b824eb808d66229f3f55b1ea60..e64027c2bc3ade4d5a6b1e25c97faa327526c5a6 100644
--- a/runtime/bin/eventhandler_win.h
+++ b/runtime/bin/eventhandler_win.h
@@ -198,6 +198,9 @@ class Handle {
 
   void ReadSyncCompleteAsync();
 
+  DWORD last_error() { return last_error_; }
+  void set_last_error(DWORD last_error) { last_error_ = last_error; }
+
  protected:
   enum Flags {
     kClosing = 0,
@@ -222,6 +225,8 @@ class Handle {
   IOBuffer* pending_read_;  // IO buffer for pending read.
   IOBuffer* pending_write_;  // IO buffer for pending write
 
+  DWORD last_error_;
+
  private:
   int flags_;
   CRITICAL_SECTION cs_;  // Critical section protecting this object.
@@ -349,6 +354,7 @@ class EventHandlerImplementation {
   void HandleTimeout();
   void HandleAccept(ListenSocket* listen_socket, IOBuffer* buffer);
   void HandleClosed(Handle* handle);
+  void HandleError(Handle* handle);
   void HandleRead(Handle* handle, int bytes, IOBuffer* buffer);
   void HandleWrite(Handle* handle, int bytes, IOBuffer* buffer);
   void HandleClose(ClientSocket* client_socket);