Hang during TimelineEventFileRecorder shutdown

[rmacnak-google]

The tests

vm/dart/timeline_recorder_file_test
vm/dart/isolates/fast_object_copy_timeline_test/0
vm/dart/isolates/fast_object_copy_timeline_test/1

are timing out on configurations

vm-aot-linux-release-simarm_x64
vm-aot-linux-release-x64
vm-aot-obfuscate-linux-release-x64

with

PID 766244 - process
TID 766244:
#0  0x00007f0bd5a39376 pthread_cond_wait@@GLIBC_2.3.2
#1  0x0000562966af0b32 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#2  0x0000562966d3f7cd dart::TimelineEventFileRecorder::~TimelineEventFileRecorder()
#3  0x0000562966d3f87e dart::TimelineEventFileRecorder::~TimelineEventFileRecorder()
#4  0x0000562966d3aca6 dart::Timeline::Cleanup()
#5  0x0000562966c73e2e dart::Dart::Cleanup()
#6  0x0000562966aef7d7 dart::bin::main(int, char**)
#7  0x0000562966aee9fd main
#8  0x00007f0bd570d083 __libc_start_main
#9  0x0000562966aea469 _start
TID 766246:
#0  0x00007f0bd580868e epoll_wait
#1  0x0000562966af51e8 dart::bin::EventHandlerImplementation::Poll(unsigned long)
#2  0x0000562966d97057 dart::bin::ThreadStart(void*)
#3  0x00007f0bd5a32609 start_thread
#4  0x00007f0bd5808353 __clone

i.e., waiting for the monitor to be signaled but there are no remaining threads to signal it.

log