Enable the -Wundef warning for clang

webrtc/modules/video_coding/codecs/vp8/reference_picture_selection_unittest.cc

 /*
  *  Copyright (c) 2011 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 "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "vpx/vpx_encoder.h"
 #include "vpx/vp8cx.h"
 #include "webrtc/modules/video_coding/codecs/vp8/reference_picture_selection.h"
 
 using webrtc::ReferencePictureSelection;
 
 // The minimum time between reference frame updates. Should match the values
 // set in reference_picture_selection.h
 static const uint32_t kMinUpdateInterval = 10;
 // The minimum time between decoder refreshes through restricted prediction.
@@ skipping 69 matching lines @@
 
 TEST_F(TestRPS, TestWrap) {
   EXPECT_EQ(rps_.ReceivedSLI(0xffffffff), true);
   EXPECT_EQ(rps_.ReceivedSLI(1), false);
   EXPECT_EQ(rps_.ReceivedSLI(90 * 100), true);
 
   EXPECT_EQ(rps_.EncodeFlags(7, false, 0xffffffff), kPropagateAltRef);
   EXPECT_EQ(rps_.EncodeFlags(8, false, 1), kNoPropagationGolden);
   EXPECT_EQ(rps_.EncodeFlags(10, false, 90 * 100), kPropagateAltRef);
 }