Join embeder threads on Windows.

runtime/bin/dbg_connection_win.h

Index: runtime/bin/dbg_connection_win.h
diff --git a/runtime/bin/dbg_connection_win.h b/runtime/bin/dbg_connection_win.h
index 2a9feb259bfe98a6f873f0a05d128fbd03ca553c..8f5d0c6baf80fde2faaebd2981335270c0f5716c 100644
--- a/runtime/bin/dbg_connection_win.h
+++ b/runtime/bin/dbg_connection_win.h
@@ -5,17 +5,29 @@
 #ifndef BIN_DBG_CONNECTION_WIN_H_
 #define BIN_DBG_CONNECTION_WIN_H_
 
+#include "bin/lockers.h"
+#include "bin/thread.h"
+
 namespace dart {
 namespace bin {
 
 class DebuggerConnectionImpl {
  public:
   static void StartHandler(int port_number);
+  static void StopHandler(intptr_t debug_fd);
   static intptr_t Send(intptr_t socket, const char* buf, int len);
   static intptr_t Receive(intptr_t socket, char* buf, int len);
 
  private:
   static void ThreadEntry(uword args);
+  static void NotifyThreadStarted();
+  static void WaitForThreadStarted();
+  static void NotifyThreadFinished();
+  static void WaitForThreadFinished();
+
+  static Monitor* handler_monitor_;
+  static ThreadId handler_thread_id_;
+  static bool handler_thread_running_;
 };
 
 }  // namespace bin