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

webrtc/modules/audio_processing/audio_processing_impl.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AUDIO_PROCESSING_IMPL_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_AUDIO_PROCESSING_IMPL_H_
 
 #include <list>
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/function_view.h"
 #include "webrtc/base/gtest_prod_util.h"
 #include "webrtc/base/ignore_wundef.h"
-#include "webrtc/base/protobuf_utils.h"
 #include "webrtc/base/swap_queue.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/audio_processing/audio_buffer.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/audio_processing/render_queue_item_verifier.h"
 #include "webrtc/modules/audio_processing/rms_level.h"
 #include "webrtc/system_wrappers/include/file_wrapper.h"
 
 #ifdef WEBRTC_AUDIOPROC_DEBUG_DUMP
-// *.pb.h files are generated at build-time by the protobuf compiler.
+// Files generated at build-time by the protobuf compiler.
 RTC_PUSH_IGNORING_WUNDEF()
 #ifdef WEBRTC_ANDROID_PLATFORM_BUILD
 #include "external/webrtc/webrtc/modules/audio_processing/debug.pb.h"
 #else
 #include "webrtc/modules/audio_processing/debug.pb.h"
 #endif
 RTC_POP_IGNORING_WUNDEF()
 #endif  // WEBRTC_AUDIOPROC_DEBUG_DUMP
 
 namespace webrtc {
@@ skipping 150 matching lines @@
     bool transient_suppressor_enabled_ = false;
     bool first_update_ = true;
   };
 
 #ifdef WEBRTC_AUDIOPROC_DEBUG_DUMP
   // State for the debug dump.
   struct ApmDebugDumpThreadState {
     ApmDebugDumpThreadState();
     ~ApmDebugDumpThreadState();
     std::unique_ptr<audioproc::Event> event_msg;  // Protobuf message.
-    ProtoString event_str;  // Memory for protobuf serialization.
+    std::string event_str;  // Memory for protobuf serialization.
 
     // Serialized string of last saved APM configuration.
-    ProtoString last_serialized_config;
+    std::string last_serialized_config;
   };
 
   struct ApmDebugDumpState {
     ApmDebugDumpState();
     ~ApmDebugDumpState();
     // Number of bytes that can still be written to the log before the maximum
     // size is reached. A value of <= 0 indicates that no limit is used.
     int64_t num_bytes_left_for_log_ = -1;
     std::unique_ptr<FileWrapper> debug_file;
     ApmDebugDumpThreadState render;
@@ skipping 211 matching lines @@
   std::unique_ptr<
       SwapQueue<std::vector<int16_t>, RenderQueueItemVerifier<int16_t>>>
       agc_render_signal_queue_;
   std::unique_ptr<SwapQueue<std::vector<float>, RenderQueueItemVerifier<float>>>
       red_render_signal_queue_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AUDIO_PROCESSING_IMPL_H_