Enable the -Wundef warning for clang

webrtc/system_wrappers/source/aligned_malloc_unittest.cc

 /*
  *  Copyright (c) 2012 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 "webrtc/system_wrappers/include/aligned_malloc.h"
 
 #include <memory>
 
-#if _WIN32
+#ifdef _WIN32
 #include <windows.h>
 #else
 #include <stdint.h>
 #endif
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 // Returns true if |size| and |alignment| are valid combinations.
 bool CorrectUsage(size_t size, size_t alignment) {
   std::unique_ptr<char, AlignedFreeDeleter> scoped(
       static_cast<char*>(AlignedMalloc(size, alignment)));
   if (scoped.get() == NULL) {
     return false;
@@ skipping 42 matching lines @@
 }
 
 TEST(AlignedMalloc, AlignTo128Bytes) {
   size_t size = 100;
   size_t alignment = 128;
   EXPECT_TRUE(CorrectUsage(size, alignment));
 }
 
 }  // namespace webrtc