Provide chrome the option of learning the debug stub port chosen by nacl.

src/trusted/debug_stub/transport.h

Index: src/trusted/debug_stub/transport.h
diff --git a/src/trusted/debug_stub/transport.h b/src/trusted/debug_stub/transport.h
index e4357d921ffe35f591c77a0d81ca7b58452dccf3..fb7b00ed8533c954bf8e37054a3399b8b8878afe 100644
--- a/src/trusted/debug_stub/transport.h
+++ b/src/trusted/debug_stub/transport.h
@@ -49,6 +49,9 @@ class SocketBinding {
   // Accept a connection on an already-bound TCP port.
   ITransport *AcceptConnection();
 
+  // Get port the socket is bound to.
+  uint16_t GetBoundPort();
+
  private:
   NaClSocketHandle socket_handle_;
 };