Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/tick_timer_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include <memory>
 
 #include "webrtc/modules/audio_coding/neteq/tick_timer.h"
 
-#include "testing/gmock/include/gmock/gmock.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gmock.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 // Verify that the default value for ms_per_tick is 10.
 TEST(TickTimer, DefaultMsPerTick) {
   TickTimer tt;
   EXPECT_EQ(10, tt.ms_per_tick());
 }
 
 TEST(TickTimer, CustomMsPerTick) {
@@ skipping 99 matching lines @@
   tt.Increment(16);  // Total increment is now 17.
   EXPECT_TRUE(cd->Finished());
 
   // Further increments do not change the state.
   tt.Increment();
   EXPECT_TRUE(cd->Finished());
   tt.Increment(1234);
   EXPECT_TRUE(cd->Finished());
 }
 }  // namespace webrtc