Enable the -Wundef warning for clang

webrtc/tools/event_log_visualizer/plot_protobuf.h

 /*
  *  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.
  */
 #ifndef WEBRTC_TOOLS_EVENT_LOG_VISUALIZER_PLOT_PROTOBUF_H_
 #define WEBRTC_TOOLS_EVENT_LOG_VISUALIZER_PLOT_PROTOBUF_H_
 
+#include "webrtc/base/ignore_wundef.h"
+RTC_PUSH_IGNORING_WUNDEF()
 #include "webrtc/tools/event_log_visualizer/chart.pb.h"
+RTC_POP_IGNORING_WUNDEF()
 #include "webrtc/tools/event_log_visualizer/plot_base.h"
 
 namespace webrtc {
 namespace plotting {
 
 class ProtobufPlot final : public Plot {
  public:
   ProtobufPlot();
   ~ProtobufPlot() override;
   void Draw() override;
   void ExportProtobuf(webrtc::analytics::Chart* chart);
 };
 
 class ProtobufPlotCollection final : public PlotCollection {
  public:
   ProtobufPlotCollection();
   ~ProtobufPlotCollection() override;
   void Draw() override;
   Plot* AppendNewPlot() override;
   void ExportProtobuf(webrtc::analytics::ChartCollection* collection);
 };
 
 }  // namespace plotting
 }  // namespace webrtc
 
 #endif  // WEBRTC_TOOLS_EVENT_LOG_VISUALIZER_PLOT_PROTOBUF_H_