linux and chromeos: Turn on -Wunused-const-variable.

chromeos/dbus/modem_messaging_client_unittest.cc

Index: chromeos/dbus/modem_messaging_client_unittest.cc
diff --git a/chromeos/dbus/modem_messaging_client_unittest.cc b/chromeos/dbus/modem_messaging_client_unittest.cc
index 506ef9bf97aef9a48f43f9e653a9627097a3f457..e0c72217284cb94d56bebc4d3f828fd5d5087bd1 100644
--- a/chromeos/dbus/modem_messaging_client_unittest.cc
+++ b/chromeos/dbus/modem_messaging_client_unittest.cc
@@ -47,14 +47,6 @@ const char kServiceName[] = "service.name";
 // D-Bus object path used by test.
 const char kObjectPath[] = "/object/path";
 
-// Keys of SMS dictionary.
-const char kNumberKey[] = "number";
-const char kTextKey[] = "text";
-
-// Example values of SMS dictionary.
-const char kExampleNumber[] = "00012345678";
-const char kExampleText[] = "Hello.";
-
 }  // namespace
 
 class ModemMessagingClientTest : public testing::Test {