[CrOS Tether] Create proto_test_util.cc/h and move CreateTestDeviceStatus() there.

chromeos/components/tether/connect_tethering_operation_unittest.cc

Index: chromeos/components/tether/connect_tethering_operation_unittest.cc
diff --git a/chromeos/components/tether/connect_tethering_operation_unittest.cc b/chromeos/components/tether/connect_tethering_operation_unittest.cc
index cb736b23c36f2740be246a5c57d25f7d95ca33f9..12442d52a51e528e029712e9caf25b3820ba44d1 100644
--- a/chromeos/components/tether/connect_tethering_operation_unittest.cc
+++ b/chromeos/components/tether/connect_tethering_operation_unittest.cc
@@ -13,6 +13,7 @@
 #include "chromeos/components/tether/message_wrapper.h"
 #include "chromeos/components/tether/mock_tether_host_response_recorder.h"
 #include "chromeos/components/tether/proto/tether.pb.h"
+#include "chromeos/components/tether/proto_test_util.h"
 #include "components/cryptauth/remote_device_test_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -64,17 +65,8 @@ std::string CreateConnectTetheringRequestString() {
 }
 
 DeviceStatus CreateFakeDeviceStatus() {
-  WifiStatus wifi_status;
-  wifi_status.set_status_code(
-      WifiStatus_StatusCode::WifiStatus_StatusCode_NOT_CONNECTED);
-
-  DeviceStatus device_status;
-  device_status.set_battery_percentage(75);
-  device_status.set_cell_provider("Google Fi");
-  device_status.set_connection_strength(4);
-  device_status.mutable_wifi_status()->CopyFrom(wifi_status);
-
-  return device_status;
+  return CreateTestDeviceStatus("Google Fi", 75 /* battery_percentage */,
+                                4 /* connection_strength */);
 }
 
 std::string CreateConnectTetheringResponseString(