ffi/isolate_group_shared_callback_test/3 times out on reload bots.

[sstrickl]

There are new test failures on Fine. Support for enums....[vm] Fix --gc_at_throw, etc for isolate group callbacks..

The tests

ffi/isolate_group_shared_callback_test/3 Timeout (expected Pass)

are failing on configurations

vm-reload-linux-release-x64
vm-reload-rollback-linux-debug-x64
vm-reload-rollback-linux-release-x64

Trimmed down example log:

diagnostics:
Process list including children: [117127]
Trying to capture stack trace for pid 117127
PID 117127 - process
TID 117127:
#0  0x0000726893c91117 __GI___futex_abstimed_wait_cancelable64
#1  0x0000726893c93a41 pthread_cond_wait@@GLIBC_2.3.2
#2  0x00005918fdca38b2 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#3  0x00005918fde91e3d dart::KernelCompilationRequest::SendAndWaitForResponse(int, long, char const*, unsigned char const*, long, int, Dart_SourceFile*, bool, bool, bool, char const*, char const*, char const*, dart::MallocGrowableArray<char*> const*, Dart_KernelCompilationVerbosityLevel)
#4  0x00005918fde9190a dart::KernelIsolate::CompileToKernel(char const*, unsigned char const*, long, int, Dart_SourceFile*, bool, bool, bool, char const*, char const*, char const*, Dart_KernelCompilationVerbosityLevel)
#5  0x00005918fde83559 dart::IsolateGroupReloadContext::CompileToKernel(bool, char const*, unsigned char const**, long*)
#6  0x00005918fde82088 dart::IsolateGroupReloadContext::Reload(bool, char const*, char const*, unsigned char const*, long)
#7  0x00005918fde7c73e dart::IsolateGroup::ReloadSources(dart::JSONStream*, bool, char const*, char const*, bool)
#8  0x00005918fdf43a12 dart::DRT_InterruptOrStackOverflow(dart::NativeArguments)
...
TID 117128:
#0  0x0000726893d25e2e epoll_wait
#1  0x00005918fdca7408 dart::bin::EventHandlerImplementation::Poll(unsigned long)
#2  0x00005918fe1416e7 dart::bin::ThreadStart(void*)
#3  0x0000726893c94ac3 start_thread
#4  0x0000726893d26850 __clone3
TID 117240:
#0  0x00005918fdfac42a dart::GCSweeper::SweepPage(dart::Page*, dart::FreeList*)
#1  0x00005918fdf9fd01 dart::PageSpace::Sweep(bool)
#2  0x00005918fdf9d77b dart::PageSpace::AssistTasks(dart::MonitorLocker*)
#3  0x00005918fdf9ffa3 dart::PageSpace::CollectGarbage(dart::Thread*, bool, bool)
#4  0x00005918fdf940ad dart::Heap::CollectOldSpaceGarbage(dart::Thread*, dart::GCType, dart::GCReason)
#5  0x00005918fdf3e6d2 dart::DRT_AllocateMint(dart::NativeArguments)
...
TID 118944:
#0  0x0000726893c91117 __GI___futex_abstimed_wait_cancelable64
#1  0x0000726893c93e9b pthread_cond_timedwait@@GLIBC_2.3.2
#2  0x00005918fdca38a3 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#3  0x00005918fdf75b98 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*)
#4  0x00005918fdf75ce2 dart::ThreadPool::Worker::Main(unsigned long)
#5  0x00005918fdf26d59 dart::ThreadStart(void*)
#6  0x0000726893c94ac3 start_thread
#7  0x0000726893d26850 __clone3
TID 118947:
#0  0x0000726893c91117 __GI___futex_abstimed_wait_cancelable64
#1  0x0000726893c93e9b pthread_cond_timedwait@@GLIBC_2.3.2
#2  0x00005918fdca38a3 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#3  0x00005918fdf75b98 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*)
#4  0x00005918fdf75ce2 dart::ThreadPool::Worker::Main(unsigned long)
#5  0x00005918fdf26d59 dart::ThreadStart(void*)
#6  0x0000726893c94ac3 start_thread
#7  0x0000726893d26850 __clone3
TID 120337:
#0  0x0000726893c91117 __GI___futex_abstimed_wait_cancelable64
#1  0x0000726893c93a41 pthread_cond_wait@@GLIBC_2.3.2
#2  0x00005918fdca38b2 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#3  0x00005918fdf9b82d dart::ParallelMarkTask::RunEnteredIsolateGroup()
#4  0x00005918fdfa4300 dart::SafepointTask::Run()
#5  0x00005918fdf75a87 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*)
#6  0x00005918fdf75ce2 dart::ThreadPool::Worker::Main(unsigned long)
#7  0x00005918fdf26d59 dart::ThreadStart(void*)
#8  0x0000726893c94ac3 start_thread
#9  0x0000726893d26850 __clone3
TID 120400:
#0  0x0000726893c91117 __GI___futex_abstimed_wait_cancelable64
#1  0x0000726893c93e9b pthread_cond_timedwait@@GLIBC_2.3.2
#2  0x00005918fdca38a3 dart::ConditionVariable::WaitMicros(dart::Mutex*, long)
#3  0x00005918fdf75b98 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*)
#4  0x00005918fdf75ce2 dart::ThreadPool::Worker::Main(unsigned long)
#5  0x00005918fdf26d59 dart::ThreadStart(void*)
#6  0x0000726893c94ac3 start_thread
#7  0x0000726893d26850 __clone3

/cc @rmacnak-google