Use ARRAYSIZE_UNSAFE when using types defined in a function

Small followup from https://codereview.chromium.org/423333002

This allows the test to compile on a greater range of toolchains (some
of which break when using types defined in a function with arraysize).

Review URL: https://codereview.chromium.org/456403002

Cr-Commit-Position: refs/heads/master@{#289051}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289051 0039d316-1c4b-4281-b951-d872f2087c98

net/quic/crypto/crypto_utils_test.cc

@@ -93,7 +93,7 @@ TEST(CryptoUtilsTest, TestExportKeyingMaterial) {
     },
   };
 
-  for (size_t i = 0; i < arraysize(test_vector); i++) {
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(test_vector); i++) {
     // Decode the test vector.
     string subkey_secret;
     string label;