Fix a crash in the event tracing shutdown path

webrtc/base/event_tracer.cc

 /*
  *  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.
  */
 #include "webrtc/base/event_tracer.h"
@@ skipping 179 matching lines @@
   std::vector<TraceEvent> trace_events_ GUARDED_BY(crit_);
   rtc::PlatformThread logging_thread_;
   rtc::Event shutdown_event_;
   rtc::ThreadChecker thread_checker_;
   FILE* output_file_ = nullptr;
   bool output_file_owned_ = false;
 };
 
 static bool EventTracingThreadFunc(void* params) {
   static_cast<EventLogger*>(params)->Log();
-  return true;
+  // False indicates that the thread function has done its job and doesn't need
+  // to be restarted again. Log() runs its own internal loop.
+  return false;
 }
 
 static EventLogger* volatile g_event_logger = nullptr;
 static const char* const kDisabledTracePrefix = TRACE_DISABLED_BY_DEFAULT("");
 const unsigned char* InternalGetCategoryEnabled(const char* name) {
   const char* prefix_ptr = &kDisabledTracePrefix[0];
   const char* name_ptr = name;
   // Check whether name contains the default-disabled prefix.
   while (*prefix_ptr == *name_ptr && *prefix_ptr != '\0') {
     ++prefix_ptr;
@@ skipping 55 matching lines @@
   RTC_DCHECK(old_logger);
   RTC_CHECK(rtc::AtomicOps::CompareAndSwapPtr(
                 &g_event_logger, old_logger,
                 static_cast<EventLogger*>(nullptr)) == old_logger);
   delete old_logger;
   webrtc::SetupEventTracer(nullptr, nullptr);
 }
 
 }  // namespace tracing
 }  // namespace rtc