[CrOS Tether] Add the notion of a tether DeviceState.

chromeos/network/network_connection_handler.cc

Index: chromeos/network/network_connection_handler.cc
diff --git a/chromeos/network/network_connection_handler.cc b/chromeos/network/network_connection_handler.cc
index 81d3492a47e1bb2af29b7fadf0690cb0785d85c7..344c570b7e833293fe894bba5a3a40427d73da9f 100644
--- a/chromeos/network/network_connection_handler.cc
+++ b/chromeos/network/network_connection_handler.cc
@@ -118,6 +118,8 @@ const char NetworkConnectionHandler::kErrorCertLoadTimeout[] =
 const char NetworkConnectionHandler::kErrorUnmanagedNetwork[] =
     "unmanaged-network";
 const char NetworkConnectionHandler::kErrorActivateFailed[] = "activate-failed";
+const char NetworkConnectionHandler::kEnabledOrDisabledWhenNotAvailable[] =
+    "enabled-or-disabled-when-not-available";

[stevenjb, 2017/04/20 20:01:10]

nit: I would just make this 'not-available'. The caller knows that it was
attempting to enable or disable.

[Kyle Horimoto, 2017/04/20 20:49:19]

Done.

 
 struct NetworkConnectionHandler::ConnectRequest {
   ConnectRequest(const std::string& service_path,