[Mojo] mojo_native_viewport_service should use "--" args

mojo/services/public/cpp/native_viewport/lib/args.cc

Index: mojo/services/public/cpp/native_viewport/lib/args.cc
diff --git a/mojo/services/public/cpp/native_viewport/lib/args.cc b/mojo/services/public/cpp/native_viewport/lib/args.cc
index 7831cad6bb41ccc8d01458b776bc8f49c195d4dd..cf0617dff5061dce7643ad0df865c08fa2c27743 100644
--- a/mojo/services/public/cpp/native_viewport/lib/args.cc
+++ b/mojo/services/public/cpp/native_viewport/lib/args.cc
@@ -8,8 +8,8 @@ namespace mojo {
 
 // Loads an app from the specified directory and launches it.
 // Force gl to be initialized in test mode.
-const char kUseTestConfig[] = "use-test-config";
+const char kUseTestConfig[] = "--use-test-config";
 // Create native viewport in headless mode.
-const char kUseHeadlessConfig[] = "use-headless-config";
+const char kUseHeadlessConfig[] = "--use-headless-config";
 
 }  // namespace mojo