Enable the -Wundef warning for clang

webrtc/voice_engine/network_predictor_unittest.cc

 /*
  *  Copyright (c) 2014 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 <math.h>
 
 #include <memory>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/voice_engine/network_predictor.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
 namespace webrtc {
 namespace voe {
 
 class TestNetworkPredictor : public ::testing::Test {
  protected:
   TestNetworkPredictor()
       : clock_(0),
@@ skipping 10 matching lines @@
   EXPECT_EQ(32, network_predictor_->GetLossRate());
   clock_.AdvanceTimeMilliseconds(1000);
   network_predictor_->UpdatePacketLossRate(40);
   float exp = pow(0.9999f, 1000);
   float value = 32.0f * exp + (1 - exp) * 40.0f;
   EXPECT_EQ(static_cast<uint8_t>(value + 0.5f),
             network_predictor_->GetLossRate());
 }
 }  // namespace voe
 }  // namespace webrtc