Fix -Wunused-variable warning if building with V8 snapshots disabled.

Bug: chromium:803591
Change-Id: I4dbbe52ca296e7232ad3eb225a2bdd84dcd0fa81
Reviewed-on: https://pdfium-review.googlesource.com/27730
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/testing/unit_test_main.cpp b/testing/unit_test_main.cpp
index d0c4dfd..88855c8 100644
--- a/testing/unit_test_main.cpp
+++ b/testing/unit_test_main.cpp
@@ -64,9 +64,9 @@
 
 #ifdef PDF_ENABLE_V8
   std::unique_ptr<v8::Platform> platform;
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
   static v8::StartupData* natives = new v8::StartupData;
   static v8::StartupData* snapshot = new v8::StartupData;
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
   platform = InitializeV8ForPDFiumWithStartupData(argv[0], std::string(),
                                                   natives, snapshot);
 #else  // V8_USE_EXTERNAL_STARTUP_DATA