Test defined(CHROMIUM) to fix the -Wundef warning

The CHROMIUM macro is only defined when libaom is compiled as part of
the Chromium source tree, so we need to test it with defined(CHROMIUM)
to avoid the -Wundef warning.

This issue was introduced in
https://aomedia-review.googlesource.com/c/aom/+/174001.

Bug: aomedia:356830476
Change-Id: Ib53b19aa2e6a2447b201dde8a41abce08c20ce04

test/invalid_file_test.cc

diff --git a/test/invalid_file_test.cc b/test/invalid_file_test.cc
index ca17395..f4343b1 100644
--- a/test/invalid_file_test.cc
+++ b/test/invalid_file_test.cc
@@ -132,7 +132,7 @@
   { 4, "invalid-oss-fuzz-9463.ivf", "invalid-oss-fuzz-9463.ivf.res.2" },
   { 1, "invalid-oss-fuzz-9720.ivf", nullptr },
   { 1, "invalid-oss-fuzz-10389.ivf", "invalid-oss-fuzz-10389.ivf.res.4" },
-#if !CHROMIUM && !CONFIG_SIZE_LIMIT ||                  \
+#if !defined(CHROMIUM) && !CONFIG_SIZE_LIMIT ||         \
     (CONFIG_SIZE_LIMIT && DECODE_WIDTH_LIMIT >= 5120 && \
      DECODE_HEIGHT_LIMIT >= 180)
   { 1, "invalid-oss-fuzz-11523.ivf", "invalid-oss-fuzz-11523.ivf.res.2" },