basic:

• features // <catomic.h> <cthread.h> <ctime.h> for c11 features, optional for c++14/17 features
• atomic_ops.h // c11 <stdatomic.h> with other funcs
• checks.cc
• checks.h // check macros
• constructor_magic.h // class macros
• critical_section.cc
• critical_section.h // mutex locks
• platform_thread_types.cc
• platform_thread_types.h // c11 <threads.h> with other funcs
• system // compile macros
• thread_annotations.h // thread macros
• time_utils.cc
• time_utils.h // c11 <time.h> timespec and millisec
• aligned_malloc.h // c11 <stdlib.h> aligned_malloc

rtcThread:

• event.cc
• event.h // semaphore
• location.cc
• location.h // where message froms
• message_handler.cc
• message_handler.h // message handler interface
• null_socket_server.cc
• null_socket_server.h // default socket server for rtc::thread
• platform_thread.cc
• platform_thread.h // thread implement for rtc::thread
• race_checker.cc
• race_checker.h // race checker
• socket_factory.h // socket server
• socket_server.h // socket server
• synchronization // sequence checker
• thread.cc
• thread.h // rtc::thread
• thread_message.h // message interface

rtcAudio:

• arraysize.h
• numerics // safe_xxx conversion/min_max/...
• scoped_refptr.h // reference pointer, in api ver. m88
• ref_counted_object.h // same? as scoped_refptr?
• ref_counter.h
• ref_count.h
• swap_queue // for signal processing
• asm_defines.h // asm utils for signal processing
• arch.h // basictypes.h

rtcAudio from system_wrappers:

• metrics.h // metric for histogram

rtcRtp:

• arraysize.h
• numerics
• scoped_refptr.h
• random.h // random
• buffer.h // buffers, move out of rtc_base
• bit_buffer.cc
• bit_buffer.h
• // byte_buffer.cc
• // byte_buffer.h
• rate_statistics.cc // rate control, move out of rtc_base
• rate_statistics.h
• rate_limiter.cc
• rate_limiter.h

rtcRtp from system_wrappers:

• ntp_time.h // timestamp utils
• clock.h
• timestamp_extrapolator.h