Lock scheme #6: Preparational work before introducing the locks in order to harmonize the code

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.
  */
 
@@ skipping 158 matching lines @@
   int WriteConfigMessage(bool forced);
 
   rtc::scoped_ptr<FileWrapper> debug_file_;
   rtc::scoped_ptr<audioproc::Event> event_msg_;  // Protobuf message.
   std::string event_str_;  // Memory for protobuf serialization.
 
   // Serialized string of last saved APM configuration.
   std::string last_serialized_config_;
 #endif
 
-  // Format of processing streams at input/output call sites.
-  ProcessingConfig api_format_;
+  // State that is written to while holding both the render and capture locks
+  // but can be read while holding only one of the locks.
+  struct SharedState {
+    SharedState()
+        :  // Format of processing streams at input/output call sites.
+          api_format_({{{kSampleRate16kHz, 1, false},
+                        {kSampleRate16kHz, 1, false},
+                        {kSampleRate16kHz, 1, false},
+                        {kSampleRate16kHz, 1, false}}}) {}
+    ProcessingConfig api_format_;
+  } shared_state_;
 
   // Only the rate and samples fields of fwd_proc_format_ are used because the
   // forward processing number of channels is mutable and is tracked by the
   // capture_audio_.
   StreamConfig fwd_proc_format_;
   StreamConfig rev_proc_format_;
   int split_rate_;
 
   int stream_delay_ms_;
   int delay_offset_ms_;
@@ skipping 19 matching lines @@
   const std::vector<Point> array_geometry_;
   const SphericalPointf target_direction_;
 
   bool intelligibility_enabled_;
   rtc::scoped_ptr<IntelligibilityEnhancer> intelligibility_enhancer_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AUDIO_PROCESSING_IMPL_H_