Pepper: Allow plugins to call PPB_UDP_Socket::SendTo multiple times.

ppapi/cpp/udp_socket.h

Index: ppapi/cpp/udp_socket.h
diff --git a/ppapi/cpp/udp_socket.h b/ppapi/cpp/udp_socket.h
index fa599d71d842e5238173d5898bc5667a01d21e2b..707c62102a17318c45c44b2672f8697b33701c9f 100644
--- a/ppapi/cpp/udp_socket.h
+++ b/ppapi/cpp/udp_socket.h
@@ -125,6 +125,9 @@ class UDPSocket : public Resource {
   /// been sent; otherwise, an error code from <code>pp_errors.h</code>.
   /// <code>PP_ERROR_NOACCESS</code> will be returned if the caller doesn't have
   /// required permissions.
+  /// <code>PP_ERROR_INPROGRESS</code> will be returned if the socket is busy
+  /// sending. The caller should wait until a pending send completes before
+  /// retrying.
   int32_t SendTo(const char* buffer,
                  int32_t num_bytes,
                  const NetAddress& addr,