Revert of Loosening the coupling between WebRTC and //third_party/protobuf

webrtc/modules/audio_coding/audio_network_adaptor/debug_dump_writer.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 "webrtc/modules/audio_coding/audio_network_adaptor/debug_dump_writer.h"
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/ignore_wundef.h"
-#include "webrtc/base/protobuf_utils.h"
 
 #ifdef WEBRTC_AUDIO_NETWORK_ADAPTOR_DEBUG_DUMP
 RTC_PUSH_IGNORING_WUNDEF()
 #ifdef WEBRTC_ANDROID_PLATFORM_BUILD
 #include "external/webrtc/webrtc/modules/audio_coding/audio_network_adaptor/debug_dump.pb.h"
 #else
 #include "webrtc/modules/audio_coding/audio_network_adaptor/debug_dump.pb.h"
 #endif
 RTC_POP_IGNORING_WUNDEF()
 #endif
 
 namespace webrtc {
 
 #ifdef WEBRTC_AUDIO_NETWORK_ADAPTOR_DEBUG_DUMP
 namespace {
 
 using audio_network_adaptor::debug_dump::Event;
 using audio_network_adaptor::debug_dump::NetworkMetrics;
 using audio_network_adaptor::debug_dump::EncoderRuntimeConfig;
 
 void DumpEventToFile(const Event& event, FileWrapper* dump_file) {
   RTC_CHECK(dump_file->is_open());
-  ProtoString dump_data;
+  std::string dump_data;
   event.SerializeToString(&dump_data);
   int32_t size = event.ByteSize();
   dump_file->Write(&size, sizeof(size));
   dump_file->Write(dump_data.data(), dump_data.length());
 }
 
 }  // namespace
 #endif  // WEBRTC_AUDIO_NETWORK_ADAPTOR_DEBUG_DUMP
 
 class DebugDumpWriterImpl final : public DebugDumpWriter {
@@ skipping 86 matching lines @@
 
   DumpEventToFile(event, dump_file_.get());
 #endif  // WEBRTC_AUDIO_NETWORK_ADAPTOR_DEBUG_DUMP
 }
 
 std::unique_ptr<DebugDumpWriter> DebugDumpWriter::Create(FILE* file_handle) {
   return std::unique_ptr<DebugDumpWriter>(new DebugDumpWriterImpl(file_handle));
 }
 
 }  // namespace webrtc