Enable the -Wundef warning for clang

NOPRESUBMIT=true
BUG=webrtc:6398

Review-Url: https://codereview.webrtc.org/2358993004
Cr-Original-Commit-Position: refs/heads/master@{#14425}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 77eab704707e03c74eda3126b92e4ef5e2b7eb4d
diff --git a/test/DEPS b/test/DEPS
index e8ed18b..969a10c 100644
--- a/test/DEPS
+++ b/test/DEPS
@@ -12,3 +12,12 @@
   "+webrtc/system_wrappers",
   "+webrtc/voice_engine",
 ]
+
+specific_include_rules = {
+  "gmock\.h": [
+    "+testing/gmock/include/gmock",
+  ],
+  "gtest\.h": [
+    "+testing/gtest/include/gtest",
+  ],
+}